A little progress on the 3599900Hz MEPT, I got the 5200500Hz local oscillator running.
Changed the plans in the progress, the second half of the 74HCT240 is now dedicated to the local oscillator and maybe a buffer stage for the 80m signal. The plan to use it as 20m driver is dropped.
Further steps, use a voltage divider to adjust the mixer drive level, couple out a tiny amount of 14MHz signal, build a 4MHz low pass and feed the result into the remaining inverters.