[Mike Taylor 3601]

Only tip I can think of is if removing balance shaft,block oil hole to bearing.
Intake tip,alot of boats w/ 4.3 have intake for 2bbl. rochester,or quadrajet, you may be able to pick some of that stuff up @ marine shop,here in KY we see alot of frozen boat engines,that you can get about anything except a block.
A non computer HEI maybe hard to come up with,can use computer version w/ ign. box like msd etc,just will have no mech. adv. if budget allowed could use digital and program timing curve
Mike Taylor3601