I wouldn't have any reservations at all.
These 86 420SELs are considered the pinacle of German marque engineering, and has a remarkable history of endurance and reliability. If you say its completely rebuilt, it ought to be as good as new, give and take a few degrees of tolerance of imperfection.
I would gladly travel with it.
This particular model caught my eye in the 80s, but to afford it then was beyond me. Such beauty.