Others have already pointed this out, but 3D cards weren't widely available until I think '96 or '97 which is outside the 486s prime years. So while you could put one in a PCI based 486 with a high-end 486, the GPU would not be well matched to the CPU. It would be more a "just for giggles" type thing.
I think someone already mentioned there was a 3D VL bus card, can't think of the name and can't see the whole thread right now. I don't think there were any others. It is possible there may have been EISA cards specifically geared towards CAD but not at a consumer price point and I'm trying really hard and can't remember any specific models, so they were either really rare, really expensive or both. I imagine the same would go for MCA.
High-end 486 systems are a strange beast, they are right at the end of the DOS era and right at the beginning of the Win 95/98 era. I had a 486-133 or 120 around 1996-1997 and it was rougly equivalent to a P60 or P75.
While at the time it felt speedy I'm not sure I'd want to take it out on the web now, I'm pretty sure it would be unuseable with all the flash/shockwave & etc.