Nothing wrong with a Muncie. An M20 is stronger than a T5OD by far. Probably better ratios too. M21 and M22 "rock crusher" are better for getting crazy with, but you'll never notice the difference in a street-driven rod, as long as you don't absolutely need an overdrive.
The trans looks good. Synchro's are not worn bad, no gear chips. Bolt it in and give 'er!
The knob could be fixed with some epoxy if it's all there.