I did my own
I converted my own and it was very involved. If I had it to do over I would go with Newman or SRII. They make a sweet product that works great. I would also use one of the companies that makes the transmission shifter (if Manual) fit in the proper hole. The biggest thing is to look at your budget, your ability and what do you want to end up with. You can go with a frame, C4 suspension and an LSX engine with a 6 speed or overdrive auto.
The strong aftermarket frames are better than the weak stock units modified. The more money the better car you will end up with. But if you want you can go to Philly Motorsports and get a C5 conversion. That is the best kind of conversion right now. It is out of my budget but that would be the ultimate!
Good Luck
Make it your own...
-Charlie