My inclination is to prefer originality when dealing with out of date machinery rather than post-period redesign - in my case it's cars, but I think/hope most owners of old aeroplanes take that view. For example, would you re-engine a Spitfire with something more powerful than and a different shape from a RR Merlin?
The de Havilland Gipsy Major engine is quite common and has a good support for overhaul, etc.