Honda recommended higher pressure on later bikes than the earlier.
CB750 Shop manual K6
Front: 32PSI / 2.2BAR
Rear: 40 PSI / 2.8 BAR
Probably due to newer tire designs. 1976 is old today
Stock setup
Front: 1.85" rim 3.25-19 tire
Rear: 2.15" rim. 4.0-18 tire
Wider 120-18 tire will get bad handling rather quick, flat .
My K6 has alu rims.
Front: 2.15" rim, 100/90-19 tire
Rear: 3.0" rim, 130/80-18 tire.
I fill a little more: 2.3/2.9-3.0 BAR
Work fine.