The 1950s Export Market
The Strv 74 and Strv 101 were only two of several tanks to enter service with Western militaries in the mid-1950s. The British Centurion medium tank, first built in 1945, had by now received several upgrades and the Mark 5 version, armed with a 20 pound gun was in service. The American M48 Patton, armed with a roughly comparable 90mm gun, entered production in 1952. Though France had little success with their AMX-50 project, the AMX-13 light tank was doing quite well. On the other end of the scale, there was still literal tons of leftover equipment from World War 2 available, such as M4s, M24s, and various other tanks. Swedish tanks would face an uphill battle in the export market, made worse by the fact that they would be fighting against American (and to a lesser extent British) political influence.
Still, there were some successes. The first, surprisingly, was not one of Sweden's fellow Scandinavian countries, but Austria. Following the end of the occupation of Austria in 1955, the neutral country needed to build up its military. Purchasing from a fellow neutral, Sweden seemed like a natural choice. The first order agreed to was a batch of Strv 74s, which narrowly won out in a competition against the AMX-13. First delivered in 1957, these would serve alongside the Austrian Army's M24 Chaffees. In later years, these tanks would receive several upgrades, much like their Swedish counterparts (though the details would be quite different). Austria's purchase of the Strv 101 was also a hard sell by Landsverk, who had to compete against the Americans' offer of M47 Patton tanks. In the end, Landsverk's marketing skills, and the 105mm gun on the Swedish tank won out, and Austria took delivery of a large order of Strv 101s. The first would be delivered in 1959; a bit later than expected, as Landsverk ramped up production.
Denmark was the next country to buy Swedish armor. During the 1950s, Denmark received many tanks cheaply from the US and other NATO allies through the Mututal Defense Aid Program. However, many of these vehicles were outdated even upon delivery (such as the M10 Achilles, which arrived in 1955). Their Centurion Mark 3s were capable, but needed newer vehicles to support them. The Danes first chose to purchase a batch of Strv 74s, to replace their M4s and M10s still in service. The Strv 74s would serve alongside the American built M24 Chaffee in Danish service. Designated Strv 74D, the tanks had several differences from their Swedish counterparts, mainly to improve NATO compatibility (these included replacement of the 6.5mm guns with 7.62mm guns, installation of an American radio, and other minor changes). Swedish attempts to sell the Strv 101 to the Danes were unsuccessful for the time being, the Danish government being unwilling to replace their Centurions so soon after buying them (in any case, the Centurion Mark 3 was still a very capable tank in the 1950s).
Unlike their Danish counterparts, the Norwegian Army chose not to acquire any Strv 74s, seeing their M24s as sufficient in the light tank role for the time being. However, they were convinced to purchase a small batch of Strv 101s. By far the heaviest tanks operated by the Norwegian Army up to that point, the Strv 101s (first delivered in 1959) were deployed in Finnmark, near the Soviet border (rumors of cooperation with Swedish units just south of the border were obviously false). Like other Swedish tanks bought by NATO countries, the Norwegian Strv 101s had their secondary guns replaced with NATO standard 7.62mm guns, and also had new radios and other equipment fitted for compatibility with American equipment.
The last country to buy the Strv 74 and Strv 101 during the 1950s was another neutral nation. Since the end of World War 2, Finland operated a bizarre variety of armored vehicles, including old Soviet and German tanks such as the T-26, Panzer IV J, and StuG III. It did not take a military genius to realize that a Panzer IV or T-26 would be deathtraps against a T-55 or T-10. The Finns, hamstrung by their treaties with the Soviets, could not purchase the newest American equipment (the Americans weren't eager to sell to the Finns in any case). The British offered the Finns surplus Comet and Charioteer tanks, and the offer was given serious consideration. But at about the same time, the Swedes offered the Strv 74 and Strv 101, with a slight discount thrown in. As the Swedish tanks were much newer, and the Soviets
might be a bit more accepting of buying arms from a "neutral" country, the Finns accepted. Though the deal was signed in 1958, the Finnish order would not arrive until 1961/62 (the Finns had agreed to accept lowest priority on their order in exchange for a lower price). Though the amount of tanks purchased by the Finns was quite small, it was still enough for them to dispense with almost all their outdated equipment from the last war.
A few other countries briefly expressed interest in Swedish tanks during the 1950s, but none made an actual purchase. The Australian government went so far as to send representatives to Norrland in 1959 to evaluate the Strv 101 in the field, but decided to stick with their Centurions. The Americans managed to obtain a secondhand Strv 74 and Strv 101 from Denmark and Norway for examination in 1960. Attempts to sell to South American countries were unsuccessful at this point; even as late as 1960 cheap war surplus M4s and M24s were good enough for that continent.
Background:
Austria, Denmark, and Finland all bought expensive military hardware from the Swedes OTL (the J35), and the Norwegians are a fellow Scandinavian country. The Australians actually considered buying J35s, but ended up getting the Mirage III instead;
https://recordsearch.naa.gov.au/SearchNRetrieve/Interface/ViewImage.aspx?B=199194&S=1 (relevant section starts page 69)
Site on Danish Army Vehicles:
http://www.armyvehicles.dk/daarmyveh.htm
Site on Finnish Military Equipment 1918-1945, include pages on various tanks in Finnish service:
http://www.jaegerplatoon.net/MAIN.html