i would still yank the intake and make sure that plug at the back of the drivers side lifter galley isn't missing. never the less the bottom end is bad. looks like trash ran thru the engine or it was put together dirty. too much rpm with half groove mains and low oil pressure/supply ain't good. if the cylinder bores aren't wrecked i'd just clean the bottom end good, ring and bearing, and drive it some more.
I forgot that plug once on a 360. During the cam break in, the lifters were rattling and the oil pressure dropped from about 50# to about 10# IIRC. Pulled the distributor and oil pump gear to get the pre-lube shaft in and when I started, there was no mistaking the flood of oil coming out the rear of the left side galley! Haven't forgotten one of those since (have found new mistakes to make).
