These are fun engines to work on, and real confidence builders. Remember one thing that won't be obvious when you're working with the clutch basket: the oil pump, at the front on that same side of the engine, has a couple of bolts that MUST come out before the clutch basket can move out. The oil pump's shaft (it's an offset arm, really) is driven from the same shaft the clutch is on, and the oil pump and it's "arm" comes off (and goes back on) with the basket, as a "group". The piston in the pump is stroked back and forth with the rotation of the clutch.
Sadly, I have seen more than one bent arm and split oil pump over this "secret" situation.
And, you can tell the early, high-performance 350 engines apart from the later, more reliable ones right here. The early ones had a smaller diameter oil pump and piston, I think it was 16mm diameter. The later ones have a larger, like 19mm, pump diameter. I don't think they were interchangable, because the mounting bolts were spaced further apart on the later ones.
But, there's 3 more HP in the earlier ones, if the transmission has survived. It was usually the casualty of the lower oil flows. The earlier cams had more lift and dwell than the later ones, too.