Get a catalogue from
www.lmctruck.com. You'll find the difference in A/C parts. You can swap it in.
You can use the stock A/C setup. Adaptors are available to properly route the hoses for use.
77 LS install
http://www.hotrodlane.cc/77chevytruck/77chevy.htm
You can also use a early 90's style compressor and bracket.
http://www.maliburacing.com/forum/vi...hp?=34&t=79059
I would use the LS compressor. It is more efficient and will last longer.
A new condensor should be a crossflow type. If you buy one, check that it's a true cross flow for R134.