Lifter stuck?

If that #8E lifter was chewed out at the end like you describe, then that is a LOT of metal that has gone into the engine. The smart thing to do is to at least get the pan and intake off and inspect and clean, and it's smater to do like you suggest and tear down and boil; there is for sure a TON of metal trash in there. The oil pump has likely pulled in some metal bits and needs replacing IMHO and who know if a few metal bits have dropped into bores and worked their way up onto the piston skirts.

Do you recall if that lifter originally slid into its bore tight? Once you get into it, I'd take a few other lifters and slide into that bore to check fit; lifters DO have variations in diameter. Inspect it for a piece of debris from the prior failure.

And I'd not worry over the lubrication of that lifter.... the main flow into the engine goes right by that lifter first thing.

As per post #7, I've got a set of cut off vlave covers just for watching. Plus, you can mark the pushrods with chalk or grease pencil and rotate the engine over several times when it is all assembled with cam lube and see the pushrods rotate that way.

Can you list your last cam and the valve springs used?