The Chrysler 360 is a
very tunable motor. New long blocks is certainly an good option. I highly recommend that if you do this, you update the ignition system to electronic CDI ignition, rather than the points-triggered coil which was standard. The regular conversion kits for the 273/318/340/360 V8 motors is only $226, including new distributor from MoPartsracing, part # P3690426. This alone will increase fuel efficiency by 12-15%.
This is NOT a marine distributor, put without points, the difference is unimportant, and you save $250 over a Mallory CDI marine distributor.
For other stuff, you can go to
Hurrikain Marine or
Ebasic Power for lots of Chrysler marine parts and stuff.
__________________
Common Sense is learning from your mistakes. Wisdom is learning from the other guy's mistakes.
Fr. Frank says:
Jesus liked fishing, too. He even walked on water to get to the boat!
Currently without a SeaCraft 
(2) Pompano 12' fishing kayaks
'73 Cobia 18' prototype "Casting Skiff", 70hp Mercury