I see what your saying, your basing the sweet spot off of the BSFC. Correct me if I'm wrong, but unless you have a CVT, you want the gear spacing to be such that you shift at max HP and when engaging the next gear you don't drop below max torque?
i was basing my idea of the sweet spot on a little of everything.
5,200 285.7 288.6 118.2 0.46at 5200 rpm, the torque and horsepower are at their closest in the entire band. yet on a shift, using a close ratio manual transmission(which most all smallblocks use) the rpm will drop no more than 200 or 300 rpm, keeping the curves nearly the same.
i was also basing it on the fact that i had built pretty much this identical engine when i was 17 years old, and that's what worked with my close ratio top loader 4 speed. it had a 2.78 1st gear, and that got me out of the hole nicely. i only had to run 4.10's, where most others with similar engines(both ford and chevy) were running 4.56 rears to do the same as i was.