Most people tend to use a T25 off a CA18det, its a little laggy when useing a T25 but when it comes on boost its like a friggin hurricane!

I first used a T2 from a ET pulsar and it was pretty well suited but it ran out of puff in the higher RPM range.

I have heard of people using a turbo off a toyota starlet, CT12 or something similar. They have a different flanges to the nissan/garrett turbos, they are also well suited to an A series engine.

Possibilities are limitless, all depends on your budget and degree of knowledge, and also what you intend to use the vehicle for.

As for using twin 40 DCOE's in a turbo set-up there is a member on here that developed a twin webbered turbo set up, his name is Kegs. It is possible with some good results. Shoot him off a PM.