I've attached a couple of photos that should help.
On 1925 boxes sometimes you don't have to do anything but if you have to, grind the necessary off the face of the sleeve gear where I've got the screwdriver tip
You can generally get enough without breaking into the oil holes.
The most important one to check, especially as you have repaired your gearbox, is the sprocket to case clearance.
They run very close and as you generally only put the sprocket on after the rest of the gearbox is assembled it's a pain to find the sprocket fouls the case.
We try not to break into the oil holes and have on rare occassions had to make a slightly longer spacer to get the sprocket clear of the case.
Hope this helps
Peter Thomson, a.k.a. Tommo
A.M.C.A. # 2777
Palmerston North, New Zealand.