could the intake be holding my low end down?

First off, run the compression test as suggested to see what you have in there for pistons. With 10.3 SCR (160 psi cranking compression), and a small torque cam, original Torker, and 1-7/8 headers, my 351C had no lack of bottom end torque.

What cam DO you have, OP, and was it timed properly?

L