How many speakers and what size?
 

How many speakers and what size are they in a 1988 gtu?

It varies, but my '89 has this set up stock:
Two under dash
Two in the doors (a crossover only sends lows to them)
Two 6 inch drivers in the rear (but they sit in a factory bowl so they'll fit in the 8 inch shock tower holes.

If you just get 6.5's for the doors and rears, remove the underdash types, that's what most people do.

sorry to bring up this old thread, but i wanted to know, since most ppl put 6.5's in the doors and in the back, which is wut i was planning to, do you need to rewire the crossovers that sent only lows to the doors? somehow, well it sound good if i don't?