Winston,

This project will require some work, but it is very doable. I did the same transplant 6 years ago. Bought a '82 245 diesel with a bad engine. Got it cheap. Bought another 240 of '81 vintage with a B21 engine that ran good, but a badly rusted body. The FI system was the same as your '79 B21. Being a simple FI system with no computer, the wiring issues were a piece of cake.

I simply removed the diesel engine and all the junk that goes with it. The B21 engine came with a very sick AW55 tranny, but the diesel engine had a rebuilt BW55. No problem. I used the bell housing and torque converter from the B21 engine, and the BW55 tranny from the diesel. The bell housing swap was very easy. I think there were something like 4 bolts. Once the engine and tranny assembly was ready, it dropped right into place. Kind of like it was made for this car, (which it was, the diesel was a cludge offering for a limited market). Needed to use the tranny cross member from the gas car, as well as the shifting rod. The part of the shifting linkage that comes down from the stick also needs to be swapped with the one from the gas car. The angle of these two pieces is slightly different for the two engines.

Obviously you will need to install the fuel pumps and fuel lines. I decided to swap my fuel tanks. I suspect you could just swap the fuel sender units. The one for the gas engine has the tank pump assembly as part of it. If your fuel lines are trashed like mine was, go to a place that makes up high pressure hydraulic hoses. Show them the fittings you need for the ends, tell them how long it needs to be, and ask for fuel proof hose. My guy made me a hose in about 10 minutes that only cost me $27.00. A hand full of cable ties and the new fuel line was in in about 10 minutes.

The ignition system is fairly straight forward. Most of the wiring was already in place. For example, the wires for the fuel pumps were right were they were supposed to be. Just not hooked up to anything. As for the capture nuts for the fuel pump tray, fuel filter, coil, etc., they were all there! Piece of cake. Took a little studying of the wiring diagrams in my Haines manual to understand what wire did what, but not too bad. Did a little rewiring, installed the gas engine fuel pump replay, and that was about it.

While I was doing the swap, I took the opportunity to do a major tune up on the gas engine. New timing belt, engine mounts, tranny mount, plugs, ignition wires, water pump, new hoses, front and rear seals, etc. This stuff is easy now. Having the donor car next to the receiver car makes life much easier. In fact, I had '79 245 (my daily driver) which came in handy when I forgot how something went together. When I was all done, the car started right up, and I drove it almost immediately.

Drove the car for several years before Rochester, NY rust ate it up. Car proved very reliable. Only things that reminded me of it being a diesel were the heavy springs in the front, and the odd rear end ratio. Getting the proper springs for the front will bring the front end down the inch or two. The rear end ratio was intended for the slower turning diesel. This made the car a little slower off the line, but the highway gas mileage was a little better. The slow acceleration was never a problem with us.

Good luck,