Wow you're at 2060!!! It' amazing how light 240sx's can get. 510's are around 2200-2300 off the showroom floor. After the swap I expect to still be somewhere in that range because of other lightening measures. That means you're lighter than I'll ever be, since 510's are pretty solid & basic with not a whole lot to remove to get lighter.

It's an IRS, the 510 wagon's are live rear. The rear is prone to squat on these things furthering traction issues for straight line racing, but they are great in the twisties. Wheelbase is 95.3". I was going to have a 4.11 rear ratio, but decided it would make my foreseen traction issues worse (225 wide tire if I'm lucky) & cruising rpm's a bit high, so I'm going with a 3.7 ratio. The 3.7 ratio combined with my smaller diameter wheels gives me a much better equivalent ratio than most Z's can get anyways.