The e32 is awesome man!! Love that car!
Looks like you already got some good responses over at bimmerforums
I'd have to do some research myself to find who has performance parts for the e32, google "bmw e32 performance parts" is my best advice.
Off the top of my head though, bavauto.com carries a lot of performance stuff (although, I find them to be pricey) ... autohausaz.com has very good prices, not sure how many performance parts they carry though.
Good luck, keep us posted on your customization process!
And make sure you mount a video camera in the car once you finish all the performance upgrades and go slay the dragon!