Ed,
I don't think that I have questioned your car being/not being a 26R. We all know that of the 95(ish) units produced all 400 of them are still in existence.
What I'm interested in is the Shapecraft bit. Your car does not seem to have any of the features of what we have, for as long as I can remember, thought to be Shapecraft bodywork, i.e. alluminium fastback (with/without side windows, 26R/standard front bumper) and "frenched-in" oval headlight covers, well above the bumper line.
Unless I'm missing something, none of the photos you have posted (including the upside-down race details from many years after this car was built) have any bearing on your Shapecraft claim.
btw, be as curt as you like.
Cheers,
Pete.