My husband and I are looking at a crashed 1988 300E. The
frame is intact, mostly just headlight and front fender
replacement along with some interior restoration - stuff we
can do ourselves. However, we were looking for a diesel
(to run on home-produced biodiesel). Is it possible to
swap the gas engine for a diesel with reasonable
modifications? I have never dealt with Mercedes before and
although I like the look and the durability, I don't want
to commit to something that won't turn out to be everything
I'm looking for. I'd appreciate any direction or resource
anyone might be able to provide.

IMHO this would NOT be a practical project at all. Obviously you can get this car for little or nothing. If you were simply wanting to put the car back together as a gas car, then there might be practicality, OR if the car was not crashed and you wanted to change it to diesel then MAYBE THAT would be practical, but to do both is just too much.

Secondly, the diesels used in this particular model which is referred to as a 124 series car, have aluminum cylinder heads and have not proven as reliable as the previous generation diesels which were the 123 series cars.

The 123 cars have all cast iron engines, are much simpler, and parts are much less expensive. Nice examples of these cars can be found on the market for $2000 or $3000.

I believe that for your purposes you will be much farther ahead with a car that is already a diesel. If you have a strong preference for the 124 car for some reason (many do) you are limited to just a few model years in which diesels were installed. Beware that the '86 and '87's have a problematic device on them called a trap oxidizer. These things were so bad that MB dealers were replacing these with entire new exhaust systems for free as a jesture of good will.

Good luck

I agree fully with Larry's last point.
If your objective is to burn bio-diesel; I would think you would be best off to look for a diesel. Why spend the time and effort swapping a gasser when there are plenty of intact MB (and other make) diesels out there in running condition?
Won't collecting used vegi oil and concocting fuel be enough of an ongoing project?

I agree too. Look for a 123 diesel.. turbo would be nice.. they are cheap.. last far better.. and will run on most any thing..

The 123 cars were built from 77 to 85.. and in two general US models.. the 240D and 300D.. there are some other sizes around but they are Euro Cars brought over here.. They come in Coupes, 4 Door and my favorate the Wagon..

Ken