Transgo 48re shift kit page 6
The kit calls for the 2-3 shift holes marked as A & B to be drilled to .106", I went a little larger .116" because the customer requested FIRM shifts. The kit does not call out the 1-2 shift hole to be enlarged because most non-hotrod uses like soft 1-2 shifts. I opened up this passage to a conservative .088" or so.
Be advised, the higher you crank the line pressure, the firmer the shifts will become so stay conservative on the hole size if line pressure is going to be substantially increased.
The holes are to be drilled in the kit supplied separator plate, not the stock plate as "staged" in the picture below.