357 runs like crap!

Your carb is on the small side(for performance).What are you revving it to?My 5 speed 90 notch with a stock bottom end,iron gt-40s ,e-cam,performer rpm intake and 650 double pumper and 4-10s has gone 13.4 @104.3 on street tires(best 60ft=1.98).Whats the compression?How safe on the wideband?pig rich?have you messed with ignition timing?

I would say the first thing is the converter is too tight. Advancing the cam improved performance because it gave you more low end to help push through the converter after the shift.

Your carb is too small. IMO the heads are too small as well but that's me. You don't say what size headers or exhaust but if I were to guess I'd say 1 3/4 primaries to a 3" collector with 2 1/2" the rest of the way. Again too small

You also don't give any cam specs so there is no telling if it is a missmatch for the rest of your parts.

To put this in perspective a 347 with Vic JR jeads, Vic JR intake Holley 750 and solid roller cam 1 7/8" primaries to 3" with dumps ran 10.50's all day long for 2 years. This was with a top loader at 3100#'s. Granted the 347 is lighter than the 9.5 deck motor you've got but the cubes are pretty close.