For your deal and budget I would look at using a set of 440 6 pak forged pistons with new rings, bearings and a better camshaft and timing set. You should have the new parts balanced to that crankshaft and balancer so it doesn't shake with the new parts Make sure and use that original torque converter also as those motors are externally balanced by using weights on the converter and balancer.
Good luck, let us know what you decide to do