Steve and I worked on
our version of a Pro IV (using a 2SC1971), but it was never completed because he died. The Pro IV that is (or was) available came from NRG in New Zealand at
https://nrgkits.co.nz/....
I had got rid of the trimmer in the oscillator (by using a spare output from the 4060 (IC1) in the PLL to drive a diode pump-based inverter to give a Varicap bias supply of 33V), and we'd replaced the DIP Switches with four BCD-coded rotary switches. The switches showed the frequency that the PLL was set to, and with the bigger varicap swing, tuning the rig just involved setting the frequency on the switches!
We'd also designed a big metal flange, which provided the heatsink for the '1971 and for the two Voltage Regulators, and was earthed. It also provided a screen between the output lowpass filter and the rest of the circuit. It was a little wider than the PCB, and allowed mounting screws to be fitted through it to the case.
We had also added separate modulation varicaps, and a resistive bias network that kept the deviation the same all the way up the band. The VCO was configured so that 1.55V p-p would give 75kHz deviation - allowing the use of a precise clipper and filter to prevent overdeviation. We had plans to include this overdeviation protection on the board too.
We also had plans to add several other monitoring options - supply Voltage, temperature and so on - but never got to complete it. I had re-routed the LED drive on the PCB so that we would have had a row of bi-colour (red / green) LEDs along the front edge of the board - green would indicate "locked" and "OK", and red would be "Out Of Lock" or "Fault".
The next version (Pro V) was to include a single chip PLL, with a PIC controlling it, and a somewhat smaller PCB. I have the early sketches for this design here somewhere.....