WOW, what were the symptoms of the engine again? Noise, knocking, tapping, smoking, loooow oil pressure?
You said you sanded the INSIDE of the oil pump housing? I WOULDNT have done that, you just made the clearances in the pump pocket larger, possibly ruining it.
Check your valve spring shims, BUT, they would have a hell of a time making it from the top of the head to the bottom of the pan, its a long trip, I guess its possible, but it would have to travel/float down the head, thru the drainback hole, onto the top of the intake valley, thru the holes in that, past the top of the cam, then past the spinning rods and crank.
Valve guides? hmmmmmm, there again, hell of a time getting to the pan. Either they drop in the cylinder, or they'd have to go up and past the guide seal, and you'd have a hell of a mess.