OM-615, to woodruff key or replace timing chain?

[Phil_F_NM]

So, I've moved back to New Mexico and "Trudy," my 1972 220D needs some serious refreshing. I know the timing chain is stretched 5-6 degrees just from using the timing mark on the camshaft and the mark on the crankshaft balancer. I'm hoping that 5deg is chain alone. If it already has a woodruff key installed, then we're talking serious stretch. The car runs great though so I'm thinking it's just the original chain.
Anyway, like the thread title says, should I woodruff key the gear and refresh a few things while I'm in there or should I just roll in a new timing chain from the top?
The former is way cheaper but takes marginally more work.
The latter is the better, longer term solution but way more expensive.

The car still has great compression on all four cylinders. Still has good pickup, even at 7000+ feet altitude (I've adjusted the IP and linkage to compensate for the lower air density here.) Still needs the IP to be timed better to the engine. I know my chain stretch and black smoke tells me that.

Opinions?

Thanks all.
Phil Forrest