Shouldn't be that hard to fix. Unless there are some sorta index marks to re-index everything on the quill that it couldbe indexed by trail-and-error by eyeballing the ignition timing point vs the slots in the points plate. And you could secure the quill by Loctite and dutch-pinning. Still a crap-shot though, and it may be better to hunt up a good used camshaft. Evaluation is easy: if it looks good, it is. Ditto on the lifters. On the /5 you probably won't need to pull the flywheel to get at the oil pump rotor-- the keyway end of the camshaft will fit through the case. Tricky, but do-able (unless you were planning to do the Rear Main Seal anyway, then go for it. Remember to BLOCK THE CRANK if the flywheel comes off.
Drop the oil pan, remove the pushrods/rocker arms and the cam can be weaseled out from the bottomside without needing to pull the cylinders. Worn as that chain is you will likely need a new crankshaft sprocket and borrow or steal a good puller. Pucker up, the crank sprocket is ~$150 nowadays. If the budget doesn't allow for that, just replace the chain and plan replace the new chain sooner (30K miles instead of 50K, no biggie) along with a new $procket later.
Sounds horrendous, but it's not that bad.
The "nearing completion" has not reversed, it's taken a side-trip. Better to have found out now that later...
And a bunch of people learnt something new...
'73 R60/5 Toaster
Luddite. Not just a philosophy, a way of life...