What he said^
Every motor build I have ever done, always run the cheapest oil through it (like NAPA brand - which is Valvoline) and changed oil and filter out at 100 miles 500 miles and 1000 miles and run a nicer oil, then if you want to go big a nice synthetic after 3K miles. It ensures that if there are metal shavings in there they are no longer. And when you have a new motor breaking in there will be, to some extent.
Assembly lube, oil, white Lithium grease doesn't matter really, they all get the job done if used properly. Just using oil is fine if you are planning on running the motor right after the rebuild. You just don't want it to sit around for a couple weeks or months. I feel the same with assembly lube. Just have to make sure your outer bearing surfaces are dry and the inner surfaces are nicely lubed, you want them to spin like a greased pig. The thing that I do see a lot is people OVER lubing bearings, all you need is a very thin light coat of whatever product you are using except oil you need to be a little more generous than that.
Recently I saw someone who used white lithium and used way way too much. You only want to use as small dab on your finger and glide a nice even coat on, you should not be able to see globs of white it should be transparent. The last thing you want in your oil ports, filter, pump ... is globs of grease.
Everyone has there own ways and methods that they have learned or been taught. I learned from my father and grandfather. My grandfather built thousands of engines from the 50's - the 90's, built stock car motors back in the 60's - 70's. All I can say is I have yet to have a failed engine after any engine that I have personally rebuilt, and I have built about 15 or so motors from scratch and several partial rebuilds. It doesn't seem like a lot but most of them were my own and I drove the piss out of them
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