Take comfort in one thing: you’re rebuilding one of the most popular and prolific platforms for hot rodders in the last 20 years. You can probably throw a rock and hit someone who can legitimately help you, haha.
Rebuilding a junkyard ls (okay yours isn’t a 5.3 ) is like the rite of passage
Yes it's been very easy to get advice, that's for sure, and it's made me want to go find a junkyard core and see if I can salvage it. Not that I have anything to put it in. This is a marine application so not everything applies (or applies differently) so the complexity is in navigating what's legitimately different vs. what's Mercruiser taking advantage of the ignorant.
For example. The engine has EV6 Bosch injectors, a completely standard off-the-shelf part. A seal kit (i.e. a bunch of o rings) for the injectors is maybe $20 from Fel Pro. If you go by the Mercruiser part number for the kit it's - get this - $297. Two hundred and ninety seven dollars for sixteen tiny rubber o rings.
The photographs (just to keep it on topic) are basically all around the accessories bolted to the heads and block. A remote oil filter, the heat exchanger, the particular fuel boost pump it uses, all with weird brackets and spacers and eight different types of bolt.
Rebuilding a junkyard ls (okay yours isn’t a 5.3 ) is like the rite of passage