convert A/C to Compressor?

i've heard some guys talking about doing this when i bring up the topic of wanting to buy a York compressor but them look a lil outta my budget. and this weekedn at ITB a guy was telling me his buddy had converted his also and it worked awesome, only drawback was that he had no A/C.....(duh)....but i dont' have use my A/C anyway so i was wondering how tough and what the process is to convert my A/C pump to my compressor.....thanks guys