About the vehicle:
-1984 Toyota Pickupwith om617 turbo diesel swapped in
-Mated to toyota 5spd trans with custom adapter plate from diesel swap company.
~120k miles on engine, with ~15k miles on swap
-Aquired about a year ago
-Cannot stress enuf how beautifully this engine ran prior to breakdown
(Cold starts down to -5 F unplugged!)

So short version of the story is....the crankshaft broke at the rear main seal after significant oil leaking from the seal. Most likely due to the mounting bolts for custom adapter plate that mates the 617 to the R151 transmission coming loose (or not being torqued in the first place?)

If yall want the long version of how this all came to pass and what all symptoms led to the breakdown then i can write it out but basically what I’m really wondering from anyone who has some insight is....

What considerations do I need to take into account if were to attempt to replace the crankshaft?
What damage could have happened that I’m not seeing looking into the bottom of the engine?
How can I check?
What absolutely needs replacing if I’m installing a new crank?

Engine is already out of the truck, on a stand, and upper oil pan is removed. I also have a donor turbo crankshaft ready to gothat I was hoping to swap in.

I’m not at all new to working on 617 engines but this is my first time staring down a rabbit hole of this magnitude, so any and all insight would be appreciated. Ill post a couple photos too.

(And Yes i realize that buying someone else’s diesel swap project was my first mistake)