Wheel/tyre advice

Sorry, another question about rims and tires. I went through this forum for days and made my choice as to the type of rims and tires I want under the C10. I just want advice on the right sizes. I bought a 1971 C10 SWB stepside:



Rims are personal, but the 20 inch rims are not my cup of tea.

I want to put these rims and tires under the C10:



The C10 is equipped with 5-hole rims and is lowered 4/6.

with the current rims there are no inner fenders, I want to have them.

Have I understood correctly here on the forum that the rear axle of a 1971 is slightly wider than a pre 1970 C10? I first thought of a combination of 15 inch rims, 9J at the rear and 8J at the front. this in combination with 275/60/15 tires. (with white letters)

or is it wiser to order four rims of 8J? I want to prevent the tires from bumping against the inner fenders or outer fenders

would like some advice from experts

gr Ron