19th century Spain was pretty broke and often fighting itself (Carlist Wars). Even though they did manage to grab the northern part of Morocco (minus Tangiers), and did defeat the Moroccans in a war, any sustained campaign would have bankrupted them. But a more stable Spain might be able to grab more or all of Morocco over the course of the 19th century, providing some concessions were given to France and Britain (due to the Straits of Gibraltar being so important), so once again they'd probably have to turn Tangier into some sort of international zone.
Spain would have more people they could export to North Africa than France historically did. They'd likely be more zealous in converting locals as well.
Some went to Morocco, but I don't think expanding the territory much will get much more than what the Pied Noirs were to Algeria.
If they tried to convert the locals (this isn't 16th century Spain, this is 19th century Spain which had sizable amounts of anticlericalism), then they'd just get a huge revolt, which they'd have quite some trouble putting down (see the Rif War).
Algeria seems the easiest given historic claims to Oran. I think Morocco and Tunisia are less likely. Maybe they could take over Algeria with French support.
They did have some claim to the Oran region, which is closer to Morocco in culture in many ways (and indeed was historically often owned by the Moroccan sultans). Franco tried to acquire the region (along with the rest of Morocco) as part of his terms for joining the Axis.[/QUOTE]