I had a pair of 1036 MK1 Concentrics on my Rickman Norton 850 in 1976. However, it had an Ex Thruxton short stroke style fully hemisphered head with 34mm inlet ports, very large valves, and Omega pistons with an ex Thruxton cam. The motor will have been very similar to that used by Dave Croxford in the space frame in 1974 for 1000cc class races.
Early '77 I replaced the 36mms with a pair of 34mm Mk2 Amals. Having been nagged by everyone that the 36mms were too big. Turns out they weren't. So I had the 34s bored to 36mm. (I run 36mm Mikunis on my short stroke 750 today with a Fullauto head).
Standard practice in the '70s was to use 32mm Mk1s, bored to 33mm. JPN did that too.
A lot of the bikes ran in the production class, so the mod (cheat) wasn't visible.
Boring a 32mm Mk1 to 34mm would have most likely ended up with air flowing past the side of the slide and would not have been recommended.