Ah, found it.
I copied the actual page at the time from "Ford GT40 Superprofile"
John Allen. Part of the narration that goes with photo 23 on p38 states:-
"It was easily the most successful private entry GT40, helped by its Hewland gearbox which allowed quick changes of ratios ensuring that the car was correctly geared for each circuit visited"
I was sure I had a good authority for that. I would imagine John Allen would be right, but who's to say....
I wish I could tell you who told me that in the first place. When I was writing "Ford GT40 SuperProfile" I talked to lots of people, and picked up many snippets here and there. It must have been a reliable source, or I wouldn't have used the information. It may well have come from one of the guys who worked on AM's cars in the 'sixties.
However, there is solid documentary evidence that the GT40 could use a Hewland gearbox, and I have no reason to believe that the car which actually did so was anything other than AM2. It was, after all, easily the quickest privateer entry.
The evidence comes from the original homolgation documents for the GT40. As homolgated, the gearbox was specified as a ZF, 5-ratio. No mention was made of which ZF, but obviously it was the 5DS25 that was used. The homologation papers were the law for GT40s, and no car could race in the "sports car" (as opposed to "prototype") category unless it complied with the homologation papers. So, Hawkeye couldn't have run a Hewland - except that, with effect from 1st May 1968, the papers were amended, with sheet 224/3/2/V being issued. This stated: "Evolution - Hewland LG600 gearbox 5-speed" and "Ford H/D limited slip differential Part Number CHD4204A". A photograph of the gearbox, alas not in situ, was included for the benefit of the scrutineers who would have to ensure compliance with the rules. I really cannot imagine there was any point in homolgating the Hewland unless it was intended to be used by somebody, can you?
Just as an aside, on the same day (1 May 68), amendment No. 2/1E was issued, this covering the "stroking" of the motor, from 289 CID to 302 CID, and a photograph of the crankshaft with flywheel and damper attached was included.
Gulf GT40s have been referred to as having, on occasion, used 305 CID engines, and I regret that I have been guilty of perpetuating that myth. They didn't use 305s - but the original technical sheets prepared by JWAE showed quite clearly that they did, and this puzzled me - but who was I to argue? The 305 (used in the Mirage) was slightly too big (just over 5-litres), and in fact the "305" referred to in JWAE's GT40 paperwork was actually a misprint, and the original paperwork, which still exists and is held by the person who created it, has now had the 305 crossed out in pencil, and replaced by a pencilled "302". Don't you just love history?!!
John S Allen