We first need to know what lens you intend to use and its attachment size. This is most often 39 mm diameter Leica thread. Some lens boards are threaded or have a threaded flange attached to the board. In these cases, you simply screw the lens into the threaded hole.
Plain lens boards have a close-fitting clearance hole and are held from the top with a 39 mm diameter threaded retaining ring. Minolta lens boards are not common. So, you might have to make one or adapt an existing board from another brand of enlarger.
You might be able to use an Omega B22/B66 lens board. They are similar in size and shape to the Minolta board. The 421-017 has the 39 mm hole size. It’s 3” OD and 3/32” (0.094”) thick. It has fastening slots for the two thumbscrews that are 2.5” apart center-to-center on these Omega enlargers. It requires a 39 mm retaining ring.
You could obtain one and drill it for new mounting holes to match the span of the thumbscrews of your enlarger.
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You could also use the Omega 421-020 Lens Disc with 39mm threaded flange (intended for the B22 and B66). In this case, you don’t need a retaining ring.
Another option is to obtain a sheet of aluminum from 1/16” to 3/32” in thickness and make one to suit. It shouldn’t be greater in thickness because the threaded shank of the lens is relatively short. It must pass through the thickness of the board and still leave enough usable thread to attach the retaining ring on the top side.
