Hello flying flea,
None of the known replica or copy engines. Needle and spring and possibly the locknut are from an original English Mills assy. No venturi to date has been made with a reverse taper on the crankcase side of the assy. Note also that the machining on the sides of the venturi is styled after the S75 design and the tank top is spaced away also, but no cut out arm fitted nor air bleed hole drilled. Tank bowl is screwed into the tank top which is what the original Mills .75 Mk 1 had in both "tear drop" and "thumbnail" style tank bowls. The Irvine Mills was the only replica that chose to screw tank bowls to tops. All genuine Mills .75 Mk II's in both P75 and S75 versions used flanged bowls retained by two bend over tabs on the tank top. Early Mk II tank tops were thin and came loose and the tabs broke, later ones were thicker. The 1/4" x 40 TPI and 11/32 A/F locknut are common dimensions to all the Mills versions. Same thread size and locknuts used on the Mills 1.3's too.
Regards - Jon