Should I tear it back apart?

Should I have put an itty-bitty bit of shellac on the mount surfaces? Silicone? Tightening the bolts down doesn't help any, how tight are these even supposed to be?

I'm wondering if I could have the parts surface milled, but then that would mean i'd have to mill the gears down the same bit to fit. Not a good idea, i suppose

I don't use silicone, because it doesn't stick to metal. You can peel RTV off after it cures, so that should tell you that eventually oil will creep under it. It can send strings of residual RTV floating everywhere, and it can cause major pump problems down the road. It really likes oil pump screens.

Also, lapping with a file is not what I would call lapping. A flat steel plate, some Clover SC sompund in the realm of 1200 grit or higher and you'll have surfaces that will wring together with a half a drop of oil and you will have difficulty getting them to part. If the surfaces were not flat enough for that, then they are not flat. Even a piece of plate glass and a sheet of 600, then 1000 SC paper will do for a lap in a pinch.

Try some shellac. It's been around for 7 decades or more and they still it. Must be a reason.

HTH

Frank