From what I have observed, there are many old MD2B/etc. in the bone yard.
The Marine Exchange in Port Towsend, WA, for example, has several..

I purchased a spare starter for $75, injectors for about $15 each and a fuel
injector pump for $30...

I have also seen the old Dynastarter on some...

My point, check around the used marine equipment stores or engine
dealers/installers. They may have something that you can canabalize.

The biggest problem in the change over, will be changing flywheels.. I've
had 2 MD2Bs but have never pulled a flywheel.. Could be tough or could be
easy (you take's your chances) so try pulling the flywheel off the old parts
engine first (for practice) and see what tools may be required.

In addition to the starter and alternator, you will need the mounts for each
and the belt drive pully for the alternator. Maybe you can get the wiring
harness as well.

The manuals I have on my web site have the wireing diagrams for both the
Dynastart and the Alternator version.
http://hood.hctc.com/~esteve/private/manuals/


--
My opinion and experience. FWIW

Steve
s/v Good Intentions