Because mine didn't include the Arduino controlled DDS/display board, I am adding an AD9850 DDS and Arduino Nano clone which will use the software from AD7C. In the above two pictures, you can see the temporary course and fine tune pots sticking out the side. These will be removed once the digital VFO is working. They even included an electret microphone element which I have put into a small plastic box with a PTT button.
My first BITX40 to BITX40 QSO was with Tom VE3THR, the radios sounded very good except that the analog tuning had a lot of drift. The new version solves the drifting problem with the digital VFO.
Power output is about 7W peak or more when connected to a 13.8V power supply, but the design allows you to up the voltage to the PA to as much as 25V which will give you about 20W output (of course you will need to use a larger heat sink). Check BITX Hacks for ideas on modifying your BITX40. The Yahoo BITX20 Group covering this transceiver has moved to "groups.io" at https://groups.io/g/BITX20 . There is also a Facebook group called "Bitx40v3 40m radio kit".