Lee, I managed to measure the ends of the bolts at 3/8" (close to your 10mm hole size for the hub assembly plate - probably is 3/8" as most Vette fasteners were imperial, not metric).
As far as I can remember, the holes in the hub plate & the knuckle were the same, & the bolts were a firm push-fit.
So it is beginning to look like someone has enlarged the knuckle holes.
My guess is that the best approach would simply be to sleeve the knuckle holes down to 3/8". I would not bolt things up with the different sized holes - admittedly, it might be ok for all lateral forces & forward braking, but you can bet that one day, you'll jump on the brakes going backwards & the the whole lot will go "clunk" - then the trouble will start !
Tom Falconer of Claremont Corvette in Snodland seems to the Vette guru in the UK - might be worth touching base ?
(BTW, I can't believe you UK guys have a place called "Snodland" !! It makes some of our aboriginal place names almost sound poetic) !!!
Kind Regards,
Peter D.