A factory cab takes the place of the ROPS so the frame needs to be strong enough to do that, unless of course you build around the ROPS and leave it in place. I would still make the framing of similar material as a factory cab in case of a roll over, you don't want the cab crushing in on you and spraying broken shards of plexiglass (by the way I would use automotive safety glass and not plexi as it scratches too easily). Easiest way to get a cab idea is to go to a dealer that has a cabbed tractor in the smallest size comparable to your tractor, take photos, measurements of the framing etc and scale it down to your tractor. YES you have to have a compressor to have an AC and a condenser with fan. You could perhaps find one of the after market units like they used to sell for cars, but I haven't seen one of those un years, but assume they are still available. You would have to determine if there is room on your engine to install a compressor also and likely have to fabricate a bracket to hold it. Likely the only thing you will be able to do it put in a hot water heater and make the cab doors removable for summer time work. Put in a fan for some cooling. Dad had a combine once with a cab and only a fan in it and it was not too bad, it keep the chaff off of you.
