This is something I posted a few years ago, should be what you need? I did this work then on a set of Henry Abe pistons I acquired that were like new, but I wanted to use Honda rings.
Sorry for the delay, here's the poop for a standard CB750 (#300) piston.
61mm piston skirt diameter
60.4mm " at pin boss
2.82mm oil ring groove width
1.52mm second ring width
1.52mm top ring groove width
3.3mm oil ring groove depth
3.3mm second ring groove depth
3.2mm top ring groove depth (I imagine this is likely the same as the other two @3.3)
2.78mm oil ring width (this is an old one piece ring)
1.5mm second ring width
1.5mm top ring width
2.88mm oil ring depth itself
2.8mm second ring depth itself
2.8mm top ring depth itself
The Henry Abe pistons I used have identical top two ring groove widths as the standard 750 piston. If you use 750 compression rings on the piston TT measured, tolerance (1.59mm-1.5mm=0.09mm) is within Hondas serviceable limit of 0.18mm top and 0.15mm for the second groove
