My 1989 300SEL has been my daily driver for a while. It has many issues including (but not limited to) electrical problems, heat problems, and a broken interior door handle on the driver's door. The problems are growing in number. The engine is strong (but does have about 225K on it).

I also have a 1991 420SEL with a bad engine. It only had about 90,000 miles on it when the engine went. The interior and body are perfect.

Is it ridiculous to consider planting the engine from the 300 into the 420's body? I know they both have the W126 chassis.

Brett