I am interest in buying an AC delete for my 85 GT. I would remove the AC unit and smog pump delete. I also have an under-drive pulley on the crank. Is there a known belt size for this application or do I have to measure it and try to get a size close to what needed? I saw somewhere on here that someone was recommending a 74" belt but they didn't say if an under- drive pulley was being used.