I drive a 1985 380SE and I love the car, I have rebuilt the transmission, the front suspension and the LEFT head.
When you say the right head are you refering to this as you stand at the hood?
The timing chain is easy to "roll in" with the help of someone else.
I don't know what you are refering to as far as a "fuel injection pump", these cars have a fuel pump under the fuel tank that rarely goes bad and the CIS injection system is ine of the simplest and most reliable out there.
The 126 body is also a tank and a very safe car. I had a customer who was an epileptic, had been seizure free for 11 years (they wont even give you a drivers licence until you have been seizure free for three years), anyway he was driving down the interstate at aprox. 70 MPH in the left lane, had a seizure stepped on the gas and went off the road to the right. He hit a tree with such force that it threw the engine/transmission assembly out of the car and it landed about 75 feet away. He lived through this incident I beleive because he was
1) In a mercedes
2) In the big 126 body
3) God wanted him around a little while longer.
I think you have a very good car and I wouldn't touch it if I were you.
As someone who has rebuilt the MB tranny's and the GM 700R4
I'll tell you the MB tranny is much better engineered and built.
ASE Master Tech
1985 380 SE