Hmmm, 3/4 ton is about 9000 BTU, which seems about right. Does it do a good job? Is yours a heat pump as well, or straight AC? Also, would you do it again, and what would you do differently?
I'm thinking of going light on the insulation to mazimize space thinking a larger AC unit, maybe a 1-ton would cool quickly and stay cool (I seriously doubt I use the truck when it's cold anyway because it's why we live in FL in the first place).
I define light insulation as 1" blue rigid foam board - maybe not even that - and some paneling, or some such. Frankly, I dunno yet.