and that's where i figured you were going, but that implies you won't bother with A/C if you can't get an adequate assurance what you install will work. problem is what you consider "works" is going to be personal opinion. the A/C in my dart works great, up to ~105' outside, sitting in normal, around here, traffic. but after that it won't cool the whole interior. part of the problem is no tint on the windows and no insulation on the roof. i could do more to make it better, but for now, it "works". all the other things you may or may not do are going to affect it too. if you know what company A/C your using i would guess whatever size condenser they sell with the kit is what they consider minimum.