If you want to cut up the car, put the 5.0 liter Ford engine in -- that would be fun swap!

If you don't want to cut up the car, a CA18DET or SR20DET will fit without cutting the firewall. The CA18 is smaller, I here that if you turn up the boost a stocker will make more power than a stock SR20.

Your best low-buck swaps would be I think:
- turbo an A15, especially if you are good at fabricating parts (for the turbo plumbing)
- the KA24E or KA24DE. This has the intake on the right side. Twistex's is running dual side-drafts (see the Shasta 2003 pics). You can get one out of a Nissan pickup

All of these can get you a 13-sec car.

no, have you seen the Tech Section article What's the best engine to put into a 1200?