904 or Powerglide???

I agree. under 2500lbs a glide will be faster. But I also think the convertor and gear will need to be addressed. If this is serious, have the engine dyno'd first. Then order the trans, the gears, and the convertor. I would think you would be better with somewhere around a 5500 stall and 4.56s or 4.88s but the dyno will tell you where the torque and HP peaks are and what they look like.