I do agree that the 05-06 is the best option many type r upgrades were added in 2005. sans flywheel, pistons, interior, trans but they did improve many things including the chassis itself. beware of a bad 2nd or 3rd gear this is a common failure but easy to fix with time and cash and while your in there you may want to add an LSD as no usdm model has one. cheers and GLwelcome to k20a.org and thank you for registering. I'd suggest moving your thread to the classifieds in the want to buy section.
I think the 2006 has a better chassis meaning rigid, better fuel tank set up than 02 04 and it allows you to run the exhaust straight back if you tunnel. this will allow you to run a header with a megaphone and it can 90 left around the fuel tank. this way your exhaust wont be dragging on the ground if you lower it.
the 06 has a better ps pump by 9%, better designed steering rack. prc cams, 4.7fd.