I want to know if I can put an 84 or a straight axle frame under my 89 truck. I am wondering if all the body mounts, rear axle,motor/trans., and bumpers would match up on the older frame.

 

Yes. Everything match up exactly. No.

Lot of work regardless.

 

what are some thing that won't match up? Cab mount? I am just trying to figure out if it would be easier to do the SAS or change the frame completely.

 

do the sas, or if you have a sfa donor truck, that has been rolled or anything, just put your caband bed on the donor truck. to do a full frame swap, you have to do alot of 'pita' work, like brake lines, gas lines, pulling the engine, tranny, transfer case, and axles etc.

 

The only things that dont match up are the cab mounts.
The rest is just tedious work. Transferring brake lines, fuel lines, and the like.