Interesting that apparently an upright Alison will fit in the cowl space of an inverted DB605.
Well the Merlin did in the Bouchon and the Merlin also fitted where an Allison did in a small production model of the Mustang used by the Americans (the P 51) and also into the P40 Kittyhawk. The Merlin was also fitted to a Bf109 by the Germans so it seems the three were with some work interchangeable
The regulatory acceptance isn't much of a problem, as these aircraft are all flown under an 'experimental' (or whatever terminology the local authority uses) Airworthiness certificate, which reduces certification costs. It wouldn't be any different to manufacturing WW1 engines, which is happening at a couple of places here in NZ.Ho Tomo,
I love the Fiets, and also think the Reggainnes and Macchi's should be back in the air, too. I believe tehre is a market for a DB-600 series engine for warbirds that could be used in lieu of the DB 600 vut which lends itself to the lines. The problen would be getting it acctepted by the aviation requlatory bodies of the world. Not sure if the market would support the cost of getting it into service, but I think probably so.