if i´d start over from scratch, i´d try a 4.25" crank from BPE. Gives you about 440 ci with a .020" over 340 block, should make a nice flat torque curve. If you don´t need to rev over 6500 then the piston speed is ok with a good quality piston and this stroke length. A set of ported Aluminium Heads will keep the package light and make some serious power, cam as mentioned above and a dual plane intake will keep it real streetable and torquey.
I agree with getting in contact with IMM engines. He can hook you up for sure.
Michael
