I know this is a day late and a dollar short, but thought I should add this to the thread-
Imho, Allen Millyard is kinda like the UK motorcycle equivalent to Pete Aardema. He's been building some very cool custom V engines from pairs of other engines for a long time. It might be of interest for another project like yours, just in case someone had to have a V12 or similar that was might fit within a smaller space.
https://www.motorcyclistonline.com/w...-12-motorcycle