I just got my '90 CQ 20v over the summer and wondering Which engine swaps are available or how to turbo the stock 7a motor?

 

You can get almost any 5cyl turbo motors and stick them in. Or you can try and put a turbo on your own. Get a head spacer (isnt ideal) or new pistons (ideal) to lower the compression.
It all depends how much cash you want to spend.
It also depends where you live, and what fuel available? LPG (propane)?