Kenwood TK-981 45W
There has been some interest expressed (primarily by me) in upgrading a TK-931 to 30W or better.
Later model TK-981's use the Mitsubishi RA20H8994M 20W P.A. module. There is a RA45H8994M1 45W P.A. module available.
All the relevant specs are identical. The 45W module needs 3.4V VDC njected on the RF input, whereas the 20W module doesn't, so we'd need a mod for that.
The two 0.22 ohm current sensing resistors would need to be changed so the current detector circuit still does it's thing.
The MA4PH633 diode in the RF switch should be OK. I haven't found a datasheet for it, but it is used in the TK-5710, which is a 110W radio in the 136-174Mhz range.
The physical dimensions are within a millimeter of being the same.
The only issue I can see is maybe needing a thermally regulated fan, or folding back power on heat (thermistor in the power detect circuit maybe?)