You should try a real engine, like a boosted 4G63
Nice work, looks like it's done pretty well!
Swapping engines in this thing is pretty easy. I'm really into the Slant 6 thing right now, but I could easily set it up for just about any RWD engine combination.
As I get more into the Mitsubishi thing (now that I have my '78 Dodge Colt) I may very likely look at dropping a wicked fast turbo engine in it.
You can see here how the engine is mounted using a simple plate. Very easy to set up with whatever you want.