Are you sure it is worthwhile to buy a fresh MV404? I had one, and it was rather gutless (even before I bent the pushrods
), and it drank gasoline like a bathtub drain.
You might consider buying a newer bus with a diesel engine and be done with it. My current Cummins 5.9 pulls hills at a much better speed, and gets around 10 M.P.G. when driven gently.
Of course, if you have a completed conversion that you don't want to abandon, and plenty mechanical skills, it is even possible to put a diesel in the old bus. Or, as a sensible compromise, a 454 Chevy, which is much easier to find and get parts for, including hop-up parts.
I'd just hate to see you spend three grand on a replacement gasser, and be disappointed, when you could buy a ten year newer bus with a diesel for four grand.