70 D100

It sounds like you are like me, you tend to over think things, Rani.
If it were me, i would just clean the engine up and re ring it, weld the crack in the bellhousing, maybe a new clutch kit etc., take care of the safety things, re assemble everything, and drive it.
The only other thing i would do would be to convert it to power steering. That's because i'm old. lol
Years ago, i had a '81 Dodge 1/2 ton pickup with the 225 slant 6 in it with the NP 435 tranny in it, and that thing was awesome.
I trailered a lot of cars with it, and while it was no powerhouse, it did the job quite well.
It was a lot of fun with the granny low first gear.
That's one of the vehicles i wish i wouldn't have sold.
Good luck with the project, i like it!