Hint! Buy parts WHOLESALE.
I recently had issues with my engine that were going to require a large expense in parts. I found a company online that had a parts list with no prices. I called for a quote and they said they were wholesale and generally only sold to distributors. But they said they would make an exception for me.
I'm not going to name the company here because they were so nice and helped me out and I don't want to take advantage of that and swamp them with personal orders. BUT if you can locate a wholesaler and contact them, they may work with you.
3 cylinder sleeves with o-rings, 10 individual o rings, a head gasket set, 6 connecting rod bearings, 6 piston ring sets, 1 main bearing set, and an oil pan gasket for $353.
The same order at agkits.com would have cost $800 and they don't carry the piston ring sets for my engine, which would have been another $120.
My build thread:https://www.skoolie.net/forums/f11/build-thread-for-haulin-oats-and-goats-11237.html#post113500
A gal, a guy, three cats, two dogs, one rabbit, and one goat, traveling the country together.