Here's the thing about this rabbit hole, though: once the top is off, you're only a few bolts away from being able to put in a new cam chain.
mystic_1
There's that, but there's ways around it.
Very true, but it's just a few bolts, and then you'd also have the opportunity to plastiguage your crank and rod bearings.
Oh and also replace those pesky seals at the right side crank and final drive shaft. They're 40ish years old!
Plus you'd be able to clean out the grunge that accumulates below the transmission, that stuff never flushes all the way out of the sump.
AAaaand, inspect/replace your shift forks for smooth shifting.
Really, if you're going to take the motor most of the way apart anyway, why not go all the way?
mystic_1