Bob Gaines made a statement about the gears that appear to be welded on the torque converter - which I don't think was answered. The flex plate that mounts to the engine (crankshaft) should have the teeth to which the starter engages - is the flex plate in place? Lastly, there should be an engine-to-bell housing plate that acts as a shim between the two assemblies - is this plate in place?
The flex plate for the early 170/200 series looks nothing like a V8 flexplate. See pic.
But Maksim27 should answer the question about engine plate. I keep tripping over one in the shop and have no clue as to why I have it.
He should also verify that the drain plug on the converter goes through any of the holes in the flex plate.
You should also take a deep dive into the 60-68 MPC. The 200 takes a number of different starters with 65 appearing to be different than later years.
You should list your ring gear depth from block plate to ring gear. Also count the ring gear as there is more than one tooth count.