Jim, It was originally designed for the Model A ford engine. Bernard Pietenpol changed the design in 66 to a lengthened fuselage with a corvair 6 cyl engine. The plans set I am using is by Jim Wills (UK) who re-validated and modified the design to satisfy the UK PFA (now LAA). Suitable for engines Corvair, A-65, O-200, Subaru EA 81 etc.
I am still undecided as to whether I'll go the Corvair (ex USA) or a Subaru EA81. I am thinking that's something that I can wrestle with after doing the wing, empennage, fuse and Landing gear etc as either will fit on the long fuse version that I am going to build.