I love the SR20DET but I am worried about emmissions and it not being legal. Will a VQ35DET engine fit in a S13 chassis??? Any thoughts???

The VQ could fit. You might have to check the width though, since it's a DOHC V6. If you can't find a VQ35(fwd or rwd), there's also the VQ30(fwd only).

Either way, you'll need a rwd transmission, either from a 350Z, G35, or a Pathfinder(2001+). If you have a fwd motor, you'll need to relocate the starter.

The VQ is a pretty light motor, considering it's a V6. It's an aluminum block motor, and probably weighs less than the iron block KA 4-banger.

The VQs are pretty strong, too. They have iron liners, so lower the compression ratio(10:1 minimum, stock) and you'll be ready for boost. VQ30DE Maximas are already making 500hp+ on stock motors.

i have a friend with a sr20det, and it passes emmissions fine