I myself, as most know, believe in earnestly trying hard to keep things original. So, if the Bosch fuel pump fails, I'd replace it with a Bosch, the same model or one designed as a replacement. Unlike some fuel pumps, for example the notorious SU fuel pumps on early British cars, the Bosch is very reliable.
However I also live in the world (Detroit; The Motor City) where modified vintage cars are all over the place--and so are the parts to make it all happen. Many early cars (a Deuce coupe, for example) have been refitted with modern engine (350 small block Chevy crate engine, for example) and suspension bits. For many years, Detroit used mechanical fuel pumps and for the "tuners" these just don't cut it. Almost all 'rods and similar modified cars have been retrofitted with electric fuel pumps and there are a plethora (there's that word again, Mr. Madison) of sources for them. Since these are not OEM pumps they almost always need a fuel pressure regulator to balance the pump's capabilities with the needs of the engine.
A good place to start looking is:
http://www.summitracing.com and search under fuel delivery; there are pumps and regulators by Mallory, Summit, Aeromotive, and more.
http://www.jegs.com/You can also easily find the manufacturer's websites directly; Stewart-Warner and Edelbrock also make electric fuel pumps and regulators.
So, armed with the specs for what you need for a W113, and a few sources, you have the ability to find what you need. My guess is you can get good, new, high-quality parts for about half the price of the Bosch. Your issue(s) will be in mounting said pump and regulator, and in ensuring you have the proper fuel line fittings; minor challenges at best for those in the realm of this consideration.
Good luck!