The F31 chassis is a modified R31 with the engine bay being near identical and the rear half of the car being changed the most.
The F31 does not have roll down rear windows and comes factory with the 280zx style rear suspension though it's possible that shock mounting points on control arms are higher or lower than on the 280zx.
You can adjust the toe on M30 rear suspension.
Even though the M30/F31/nissan leopard engine bay houses a single cam vg30 like the Z31, the dimensions of the bay are different concerning crossmember location and steering rack angle as well as steering shaft angle.
This means the M30 crossmember in a Z31 will have bolt holes that don't match and also means that simply drilling new/extra holes might be a bad idea since the inside of the box sections of the frame rails have reinforcement where the crossmember bolts through.
I would keep the Z31 crossmember, get a front sump L28 pan (1981 to 1983 maxima), and adapt the L28 for front sump pickup,
Of course, you will also need to very carefully drill a new hole in the block for the dipstick.
The M30 swap I did covers much of what is needed to do it to a Z31 except for turbo/downpipe clearance of steering shaft.
The most important dimension is whether the L28 turbo itself clears the steering shaft of the Z31 but you might get lucky like in my M30 and find the turbo and factory L28 elbow clear it just fine.
Since the L28et stock turbo has a two piece elbow, it's not hard to make a custom pipe with a 4 bolt flange that fits as well as getting rid of the two 90 degree angles used in the stock setup.
On my previous 1984 L24 turbo maxima, I made this custom pipe and reduced the two 90 degree angles to two 45 degree angles.
I guess I can try to fix up the thread posted here at some point.
The biggest change was needing to lower the engine relative to the mounts (the rubber is stock L24 maxima mounts).
I would fix the thread posted here at hybridz but ran out of patience with the forum software change a few years back.
It's a daily drive that does mid 14s in the quarter at 7.5psi on an untuned M30 ecu.........which runs 14.7 A/F ratio during daily driving and dips to 11.8 under boost with stock 280zx turbo injectors.
I'm sure that the "under boost" will get leaner the more boost I throw at it but everything's perfect at this time though I would like a more turbo friendly timing curve.
Edited by HowlerMonkey, 2 weeks ago.