727 or 904?

IMO, if you don't already have a tranny, don't spend money on a SB 727. SB 727s tend to be rarer thus more expensive. SB 904s are pretty much a dime a dozen and will be plenty strong for what you're doing. A 904 weighs less, has less rotating mass, and shifts faster than a 727. Only time I would use a 727 on the street is if I was doing some fairly heavy and frequent towing.