6.2 and 6.5 NA engines do have different calibrations.
The 6.5NA pump is likely a DB2831 pump, where the other 6.2 pumps are DB2829. the 31 and 29 are plunger size. for .290" and .310"
Any of them will work fine, no picking to it really, just match your calibration to the engine/year configuration.
If using C-Code cylinder heads from a certain year, ensure you're getting the calibration for that year engine and rating. You could turn it down some.
For injectors, Aim a little higher than the 1800-1900 6.2 Spec, say 1950 pop pressure with correct nozzles.
J
1982 C10 SCSWB 6.5TD, mods too extensive to list. (13.69 1/4 mile @94.6 MPH) RACE TRUCK
1982 C10 SCSWB 6.2NA, 2.73 700
1986 C10 SCLWB 6.2TD 3.73 700
1989 V20 SUB 6.2NA, 3.73 400
1994 G20 VAN 6.5NA, 3.42 60E
1994 K20LD ECSWB 6.5TD, 3.42 80E
1995 K20 SUB 6.5TD, Wrecked, ran into by stupid teen.
1995 C3500HD DRW 6.5TD, 12' Flatbed 5.13 80E
1995 C3500HD DRW 6.5TD, 18' Rollback Wrecker 4.63 80E
1994 C20HD ECLWB 6.5TD 3.73 80E Wifes Truck.
1995 C20LD ECSWB 6.5TD 3.73 80E
1995 K20LD SCLWB 6.5TD 3.73 80E
1996 K30 DRW 6.5TD 4.10 80E
1997 C10 Tahoe 2Door 2WD 5.7L to 6.5 Conversion Underway