thanx in advance for all input....my sons sdl engine is running real bad.i pulled it from an sdl with 268000 on it and he put 40000 plus with no problems till recently.....i dont want to put money in an engine with 300000 plus miles..the car has 170000 on it and we got it with a piston rod through the block.this weekend i bought a nice 87 300d with 127000 on it and rotted spring perches.my question is should i change the trannys,,i used wood in place of springs and drove it. it shifts perfect.fluid is nice and no crap in pan.another question is there anything else needed to swap off old engine? i still have old one with hole in side that has 130000 miles on it and looks very clean.

The speedo output from the tranny is different, so you'll either need to change the tranny tail piece or the tranny itself to install a tranny from a 124 chassis into a 126 chassis. Assuming the SDL tranny was operating fine I would swap the entire tranny rather than swapping tranny parts.

If you go that route make sure you remove the flywheel bolts before pulling the engines, it's just much easier to get at them and do that with the engine in the car rather than on the ground.