You are creepy!! People with fetishes are strange!!!
You'd just be taking it further away!!
I have to admit, someone did float the idea of going with a diesel drive train from a W123. They're are a lot around here, but not exactly any with a manual box, so I'd have to source that from elsewhere. But I could get the motor with no issue.
An OM616 or 617 would certainly make the car more future-proof as there are plenty of parts out there.
sourcing a manual transmission from a 240 and performing a manual conversion on a 617 or 616 motor is an easy and extremely well documented swap on the various MB forums.
For example, if the work of making this engine choice a manual, and the lack of a bolted together 617/616 and 4-speed ready for you to pick is a deterrent, then an alternate engine swap for this vehicle is not for you. Even with an ideal drivetrain, every single part of getting it into a chassis it wasn't designed for will be a custom experiment. You might pull and install the motor 20 times at a minimum. That can't be a pain in the a$$ for you, it has to be fun if you want to finish building something.
I would have suggested a 4.0 and 5-speed out of a Jeep, but again, getting that bolted in will be a lot of custom work.
I agree with the sentiment in the above post. It seems to me that you are more excited by the idea of driving
the conversion, than the process of actually building
it. If thats the case, selling the project seems a great idea to me. Projects of this type get completed when the process is the part someone enjoy, more than the end product.
This is the reason guys build custom cars and then sell them, they love the journey, not the destination.
People are telling you to hold onto it because you will regret it later. I say sell it and stop worrying about it. Yeah you may regret it, but you may regret sitting on a "might be if only" huge project for 20 years as well. Plus the cost of keeping it around, and the bother or worrying about it.
Everyone stalls on projects and sells them at one point or another, so no shame in that. I say move on and forget about it. There will always be a later, and the later always comes with the experience of the prior. I have sold numerous projects, and completed numerous others. I always say, "well I wish Id kept that 1965 buick and did such and such", or "I wish Id kept that 1982 grey market 300D and did such and such", but im lying to myself every time.
People forget the motivations of the actual time of sale, and for my project selling times, I made the right move, moved on, and returned later with more money, more experience, and more drive to get it done.