Even though it is a physically larger trans in all dimensions than the TKO, I think you will really want/like the T56-Magnum better. I know for sure it shifts better than the TKO esp. at high(er) rpm.

My goals here are:
- no frame cutting (if that's possible)- not possible with either trans
- fun factor (decent OD for cruising)-- either one ok T56 double OD 5th & 6th
- factory-looking shifter setup - someone else will have to answer
- will live behind this motor with street tires - T56 is better IMHO

with 500cid/500hp/550tq 1st & 2nd gear will only be needed when you want to show off. TKO/T56 both have really deep 1st gears, and only slightly less deep 2nd gears, you will be able to spin the tires very easily. You will probably find that starting off in 2nd works just as well then a quick shift into 3rd for everyday/non-spirited driving.