I'd be inclined for transportation. But, in hindsight I'd not expect the same result earlier in 1943-44 as in 1945 in Germany. Despite claims by the US 8th AF the damage to transport late war, or earlier in Italy and France, was done by the British tactical air forces or the US 9th and 12h or 15th AF with groups of medium & light bombers. Those organizations eschewed high altitude techniques & attacked the targets from medium and low altitudes. ie: fighters on railway strafing missions, or the 9th AF bombing bridges from 15,000 down to 5,000 feet vs the 20,000+ feet of the heavy bombers. Part of the problem of the low damage to German industry 1942-44 was because of the inaccuracy inherent to high altitude bombing, so I'd not expect the same results from B17s & B24s attacking railways in Germany as in 1945 when the short ranged bombers could reach Germany.
Stripping the occupied nations of their weapons had more to do with adequate weapons stocks than manufacturing. Polish and Belgian built Browning Automatic Rifles were common among second, third, & fourth tier German units, so were Czech MG, French and Soviet cannon. In 1940 ten+ recently formed German divisions were armed with former Czech rifles, MG, & artillery. Had the Atlantic Wall been stripped of non German weapons in June 1944 large swaths of it would have been unarmed.
This large scale use of foreign weapons also eased ammunition manufacturing requirements due to the stocks captured.