Hey Mick, do you have any photos of your conversion?

I narrowed the sub-frame without changing any of the suspention pickup pionts, by cutting from sub-frame ether sides of the diff.

s13 and r32 gtr sub frames are a straight swap
s14 and r33 maybe the same but im pretty shore the s13 s14 diff's are the same but not s15 anyway best of luck with it

I'll post some pics tonight. But I channeled the subframe (when I say I, I mean Kev Rowley and I. When I lived in Brisbane. I planned it and we executed it...consider him a good mate of mine) and reinforced with a fair bit of steel.
I used the S13 platform, s14 LSD, 300zx hubs and brakes and 300zx turbo axles with s14 driveshaft 'hubs' (or whatever they are called). I also created (by my own hand) some strut turrets in the tray using the s13 tops, which fortunately match the 300zx struts. No matter how hard I tried I could not reconcile rear suspension to the chassis, either direct or using an inboard system...for the travel I wanted, which was approx. 130-140mm from memory. I have all of the chassis diagrams matched up if that would help.
I strongly recommend getting the diagrams from the IRS you are using and referrencing everything to the common "ground" measurement.
It turned into quite a problem solving exercise. To be honest, hindsight says it isn't worth the trouble...but I loved the engineering exercise.
I'll PM you when I find the photos
Michael

hey maddat and micks ute , what a cool conversion i have had a s14 rear clip for years and am doing the same thing , not as far along as you guys though , as far as the top shock mounts in the tray are concerned have you thought of using a pushrod and rocker set up with the shock mounted parrellel to the ground like the formula cars do? this was my answer to not having towers in the tray. keep up the good work. oh also if you use the gtr rear upright its made of aluminium has a better vented disc and twin piston caliper , and has a drum handbrake set up , i tried a 200sx rear caliper on a previous conversion and it was a failure the hand brake not good enough

Wards
Yeah I really considered the inboard suspension with rockers etc, but in the end I couldn't design a system that worked as well as the stock version, in the space i had available...fuel tank moved behind diff for extra weight.

I have added some pics below to show you some of the packaging issues you have probably already thought of, but the pics help you see the actual amount of space you will get. The first 4 are upside when the ute was on a rotisserie.
Michael

http://datsun1200.com/modules/myalbum/photo.php?lid=19157

http://datsun1200.com/modules/myalbum/photo.php?lid=19156

http://datsun1200.com/modules/myalbum/photo.php?lid=19155

http://datsun1200.com/modules/myalbum/photo.php?lid=19158

http://datsun1200.com/modules/myalbum/photo.php?lid=19159

very cleaver engineering there
simlar comcept to XJS Jaguar rears

Crazy 1200
How the hell did you manage to put the pics in the message. I read the FAQs and THOUGHT I did what they said but obviously not quite right.
Michael

hey mick what made you come up with this idea...testing it will be fun once complete

The short explanation was that I got sick of the rear suspension. It bounces, wobbles, shakes and makes you understeer. So putting the fixed diff and cradle should add enough weight to get rid of those traits and the new design should help with complicance. I still wanted to be able to fit a surfboard, etc in the back, so I did this to a ute. I am soon to get a sedan or coupe to have something of a race car.