200lbs weight differance between the SB/904 and the BB/727 combo. Aluminum heads on the BB only make it about 50lbs closer.

If you are stuck running a stock head then common BB and SB heads flow about the same so HP will be about the same. An easy 433 SB can be had with the BPE stuff, very close to the 440 so TQ will be almost the same minus 200# of weight over the front end that impairs handling somewhat and makes it just a little harder to hook up. If you run low gear set 1st and 2nd in the 904 it will make as much TQ at the wheels (mabey even a tad more)as the 440. Another thing is the 727 soaks up about 20 more HP than a 904. With the modern SB stroker stuff being so cheap and the car is already set up with a SB I say the choice is easy. If you could afford eddy victor CNC heads(and all the expensive stuff to go along with it) and a 512 kit for the BB then I would say go BB.