With a mere 120lbs of weight gain, wouldnt it make more sense to go with the big block, use aluminum intake and connecting rods, then compensate for the extra 25lbs of weight by using the gain of somewhere around 100ftlbs of torque to get the needed air? After all, you get the wheelie on launch, and you need the low end. I personally reccomend the early 70's 454 Chevy. Lots of aluminum parts available, and little smog settings. Just a thought.