87 Base model here. I was wondering for the rear single piston calipers do I need to switch those out and replace them with the single piston that was on the GXL? Because I already know for the fronts I’m going to need to switch the singles for the 4 pistons.

 

you have 2 options, actually. the 4 piston fronts, got a vented rear, which is wider, so the caliper is different. plan B, the 89-91 base models are 5 lug, but have the base brakes, so you can swap the 5 lug, but keep your calipers.
if you have a hard time finding calipers, just buy the non vented 5 lug rear rotor and call it good

 

Thanks, and one more question if I plan to put the 88 gxl lsd in my base model would I also need the driveshaft from the gxl and would you trust a junkyard car for these parts?

 

if you do find a junkyard one, grab the driveshaft, i think yours will work. the diff's last basically forever, so that will most likely be fine

 

Sorry and another thing is would I need the CV axle from that gxl? Yeah, sorry can’t seem to find anything related to swapping things over from higher trim fc’s to the base models other than 4 lug to 5 lug.

 

the axles are just turbo and not, so no, but grab it anyways, FC's are getting to be vary rare