Surely you would had a giant bang with a catastrophic piston failure? But it does sounds like one of those crazy turbo diesel runaways you see videos about.
I would not buy someone else's modified truck because they would change it in a way they like not the way I want it.
Do to answer your question 50th is the truck I'd get.
Easier to insure and sell down the road to.
Have a galvy ashtree unit on my truck. Fitted to chassis easily. Now to bolt up the rest of the truck.
A second one didn't bolt up easily at all. Something happened in manufacturing it but customer happy