Which AC/heat system and why?

Not to get too far off topic, but for a LONG time all the MFG and most of the hobby participants thought no one had any 72 cars either, and that "the hobby" stopped after 1971. 72's have kinda crept in as people slowly figure out that styling in dang near identical to 71, and the change from gross to net HP and a slight decrease in compression wasn't a 30% drop in power.