I hesitate to respond because it's your car and your business.

I really hate to see one of the rare and fabulous 5 speed 300E's butchered up. There are MANY differences between a gas engine and diesel engine 300E. If I were of a mind to make this conversion I would not do it unless I had the entire donor car setting next to the recipient.

The M103 is a really good gas engine that will last as long or longer than the 86/87 diesel engine. It also is less expensive to rebuild and maintain.

Is there something wrong with the engine in your 300E? Unless there is something totally destroyed, it would be less expensive to rebuild that engine than the long term expense of eventually rebuilding the diesel.

It's your car and your business.

Have a great day,