They probably won't fit without spacers, and thats even if the SC400 wheels are 5x114.3 bolt pattern. Toyota likes to make their wheels +50 offset, but since its a much earlier model, you might be lucky. Check the bolt pattern.
EDIT: After re-reading the question again, I think you might be describing aftermarket rims, if I'm not mistaken. If thats the case, then chances are that the offset is lower than +50 (not very many aftermarket rims come in this offset), so you might be ok. BUT, depending on how "early 90s" the SC400 you're talking about is, it might either be 5x114.3 or 5x100. Double check. 'Cause you need 5x114.3.
