If you want to keep it in the 75 stick with red or purple. The rest need 2' width at least. Black and mala may need more if you keep them for life. If you're gonna put it in the 300 you can go with anything except lac and aimara.
As far as sticking with one wolf I'd disagree with kno4te. Unless putting two (red and purple) in the 75 forever then agreed don't do it. Maybe if you get a curu and mala and the curu is bigger, I can understand as well but with a 300 you're likely to be alright still in that case imo. I wouldn't suggest getting a red and purple together unless you have a more dominating species like a gold or Hoplias species to keep them in their place. When I first introduced my purple it tried challenging the gold and odoe by flaring but both weren't bothered with it and paid it no mind. Died down em after a few minutes and the purple followed the gold and odoe around.
Curupiras are said to get to 30". Malas 24". Biggest captive specimens I've seen or heard of was 2' for curu and 20" for mala. Vendors I purchased from for wolves is rapps and wes. Can't say I've seen either bring small golds in. You have the IDs right. There's an old ember here you should check his threads he had a large curu with some golds. I can't remember his name exactly it's something like mynheer then something else lol haven't seen the name in a while.
One thing to note. Curu is more likely to be active compared to mala.
Disagree with getting an aimara. Not for it's attitude but for its size. While it may take some years there are plenty of specimens 2'+. I suggest minimum of 8x4 for that species. Assuming they don't grow to the 4' or so that was claimed.
Dloks
ever see the picture wes posted of his friends aimara? Might wanna look into it.
My curu was more active than my purple wolf until I put the purple wolf in the same tank and it stood with the gold and odoe towards the top majority of the time. As far as purple and red, the only general difference is reds can be more territorial, but I haven't noticed it within my own specimens.