The following measurements are not accurate to the nearest 0.01mm or anything, but should steer you on the right track...
I measured an early monoshock DT175 barrel (66x50mm), monoshock DT125 barrel (56x50mm) and a late monoshock DT175 barrel (64.5x54mm).
Barrel height: 91mm
Barrel spigot diameter: 93mm
Barrel spigot depth: 27mm
Spacing between case-to-barrel studs, side-to-side: 88.5mm
Spacing between case-to-barrel studs, front-to-back: 93mm
Although I did come up with one whacky figure (stud spacing, front-to-back at 96.5mm for the early mono 175) - I'm assuming that I just screwed up the measurement. Will check tomorrow.
WRT the pistons, they all run 16mm gudgeon pins.
The gudgeon centre to top
edge (not the total height like you asked for...
) is:
35mm for a late monoshock.
30.2mm for an early piston (not 100% sure whether it was from a twin shock or early monoshock, but the Wiseco catalogue
suggests that all of the 66mm bore, reed valve 175 pistons are the same as each other).
FWIW, I also measured a MX125A barrel, YZ125C barrel and a twin shock DT175 barrel:
Barrel height: 90.2mm (this difference is likely to be my ham-fisted vernier skillz).
Barrel spigot diameter: 74mm
Barrel spigot depth: 23mm (27mm for YZ125C)
Spacing between case-to-barrel studs, side-to-side: 52mm
Spacing between case-to-barrel studs, front-to-back: 70mm
