ac compressor

I have a 88 gmc 350 5.7 and i changed the compressor with 2000 or higher compressor and i cant get i to turn on. The compressors Low pressure cut-off switch does not fit. do i need to change the switch or is there another way to fix it. how can i jump the pressure switch to get the compressor to turn

What doesn't the compressor switch fit? The connector? Did you convert the system to 134? Lots of info left out here.

I dont think so ,how do you tell. I bought it used and the ac worked. The compressor i got is for a newer truck.