What are the correct wheel size, offset, width bolt pattern etc that fit these cars?
Do you want wheels identical to the 1965 originals?
'65 wheels were unique. The chrome spokes were the normal shiny, polished chrome you are accustomed to.
At some point before 1966, the shiny chrome was replaced by a satin or 'bead-blasted' look.
'65 wheels were also painted a grey/argent silver color in recessed areas, later wheels were satin black.
I believe the offset was the same up to about 1969. At that time the back spacing was decreased to move the tire out for a wider track.
The later 70-mid 80's wheels were avail in a 15"x7" size. Typically 4-3/8" back space, 3-5/8" 'front space'...... yes 8" wide edge-to-edge, 7" wide between the tire beads. That offset works well with wider tires if you go that route..... 255's or maybe even 275's will fit.
That's a GREAT looking truck!! Nice to see that '65 GS went to a talented owner!