Hi Bud,
Ive been looking at doing this for a very long time, ive even tried talkin to nissan/ autech in japan to see if I can get the specs of the rear panels on the autech 4 door but with no luck. I was even told to order rear quarters i would need a vin number of an autech edition
Anyway i spoke to the fella who owns www.jessestreeter.com and he mentioned to me that if i can get a part number for these panels from nissan he should be able to get it, but there in lies the issue....
Il add some pics up and from what i can see the autech wider body starts from the middle of the rear doors and from what ive noticed on my 4 door there is a little bulge but no where as near as the autech.
Lemme know if you hear anything coz im interested as you can see.
Heres some of the other kits ive been looking at from japan just out of interest.
Aero Palace( http://www.aeropalace.co.jp/sports)in japan have 3 kits , Impul, BN and their own for an r33 4 door. I even thought of taking the rear quarters from the BN Kit and try to reduce the width since i didnt want the wide body look.
Heres some pics as well.