I don't see how a 351 is easier, with a heavier rotating assembly, bigger mains, and also the added weight of the block.

To the OP, if you keep it N/A do an early model block, keep the ratating assembly fairly light. Put the heads you have in the hands of the right person, an off the shelf hydraulic roller, change the intake. Keep it out of detonation, don't spin it to the moon and it will live and make 500whp.