Wheel/tire size 77 fenderside

[OxonCounty77]

Hi; I am enjoying using my 77 now she is on the road here in the UK after her previous life in Mississippi.
She desperately needs some deeper dish rims to fill out the fenders though.

Despite searching this (excellent) forum I have been unable to find the definitive answer;- I fancy fitting Vintique OE steels with theoriginal hub caps.
My supplier says go 15x8 all round with 235/75 15s. Will these be beefy enough? Can I go to 15x10 on the rear (with standard ride height)(and if so,what tire size?)

Many thanks.