70 D100

NP435 is a fine transmission, don't be too quick to get rid of it. The crack in the bell housing has likely been there since day one. Flow some brass across it if it worries you.

That slant may have been running just fine "when parked" but it looks like it has sat for a while. I'm with RRR, clean it up and see what you really have. I bet the bores clean right up with some 220 grit wet/dry and ATF. Rings, bearing inserts, timing chain, lap the valves, gasket set and and a tune up... Bob's your uncle, a runner. That's an "overhaul" not a "rebuild", but I bet you have enough left out of $1000 to do the brake hydraulics too.

Heck, I'll take the whole mess off your hands if you don't want to bother with it.