Well you've covered what I'd probably tell you to do (which is basically the timing chain,etc) with the 126...if you have the paperwork with the car, check to see if the PO already had it replaced since this should be done about every 100k miles. If its been done, you can either do it now anyway, or you'll have a little while to get to it later. I was also gonna tell you about watching the levels with your hydraulic system (my 560 having this system) but I see you have a 126 without this system.
Other than that, your baby's pretty much bulletproof although I personally have been replacing relays,etc within my engine compartment just for the heck of it because they'll eventually go since the car is 15+ years old (I keep the old parts if they're still in what I think is in pretty good shape and just put them in the new parts box and "file" them on my MB shelf-just in case). Another thing with the 126 would be the infamous radiator neck being pretty delicate and subject to breaking (you may want to pull your upper hose and check it). This is another thing I replaced as a preventive maint. issue that will help prevent you from having to spend a mint replacing your engine because the radiator blows a hose at the most unopportune time.
Are there any issues that you "see" or "hear" that concern you with the car at all?
1970 250C SOLD
1971 250C SOLD