Well...
The first thoughts that went through my head were: Why would you buy an engine, and then not run it for 5 years, then sell it again?
Now... there are several legitimate reasons that I can think of; but the one that keeps coming back to me is: He tried, but it won't go. Maybe after a bit of tinkering, he gave up & now the mrs is moaning about "that thing".
His added comments about the Start-o-Matic boxes are quite true. Looking at the state of mine, I'd be very reluctant to rely on the 1950s electronics for anything other than show use. As it happens, my SOM alternator is fritzed anyway, hence using an ST head & a flex plate w/ starter motor to start it.
IMHO - if the engine is sound, then it's certainly a good place to start. Depending on what you want to do with it, you could either restore it to its former glory for show purposes (in which case, it's about as good a place as any to get started), or strip the old electrical gubbins & replace with modern equipment; in which case you're really only interested in the engine. However... it might still be worth buying as you can always flog the SOM alternator separately to get a few bob back.
Ironically, if it's a show engine you want, Spencer's (the other one linked on this thread) might be a better start point, as it already has the water & diesel tanks, and the heavy cast iron exhaust, all of which looks to be original equipment. Spencer's also comes with a bunch of batteries you can flog to offset the cost of buying the unit. Just remember that you have to re-sleeve & re-ring it...