I have an 64 Cortina rear axle/diff which uses a nut and bolt to marry it to the prop,anyone know a source of 10.9 bolts/nuts? all I can find are standard spec ones..TIA

Presumably the bolts are imperial 5/16"?
If so the equivalent to metric Class 10.9 is imperial Grade 8
Grade 8 bolts are designated by 6 radial lines on the face of the hex head.

(Grade 5 bolts only have 3 lines)

I have just ordered a pack of 10. M10x35mm 10.9 tensile and only need 3 of them just cover the postage and I will send some to you
Cheers
mark

Thanks for the kind offer but I don't think they will fit.