The 302 will have enough torque to pull an A/C compressor without any noticeable loss of performance. Check someplace like "Vintage Air" to see if they make a compressor adapter for the GMC engine (probably not). I've seen the smaller import car compressors mounted where the generator usually goes, with the generator or alternator piggybacked on top and driven by the second groove on the compressor pulley with a short belt.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!