168,000, give or take a few; cyl heads may be relatively easy to produce, but they’re not what will be needed, its crankcases, crankshafts, camshafts, reduction gears, and cam covers with “Rolls-Royce” cast into them!

many thanks for the number stuart, i thought it wouldve been much more!

i think there may be one or two manufacturers making Merlin cranks, cams ect already, certainly though crankcases may be a problem, considering how many decent crankcases get grenaded at Reno each year