short version: 90 RS body and dash with 85 z-28 drivetrain, wiring and ECM. i used the speed sensor from the 90 transmission (electric on the tailshaft of the tranny) I need to get the 4K per mile VSS output down to 2K per mile for the 85 ECM while retaining a 4Koutput for the speedo. The easiest way seems to be the #25071437 buffer box. I've been through my local salvage yard twice trying in vain to find one. Does anyone have a list of GM vehicles this buffer was installed in beside various camaro/ firebirds (they are completely picked clean at the local salvage yard). chevythunder.com used to have a short list of some Buick models that used it but i cant find that info any more.

 

25071437. Look for any late model GM (day '87-92) that has a V8 with TBI - not TPI. I rumaged through a bunch of caddies and scored.