The mods continue. The biggest issue I found with using a Weber 38 is it use the inboard throttle shaft whereas the 32/36 uses the outboard  (primary). That means the rotation is opposite, so rather than dick around with a bellcrank (which only complicates a kickdown), I decided to make the outboard shaft work off the cable.
I had a spare 32/36 which supplied the bracket for the throttle shaft. All I had to do (so far) is grind the staking off the old shaft, drill it to use the little hub on the new "gear" as a center, drill and tap the new shaft to hold the bracket on, and clearance the ear on the throttle spring. I have one more fastener to design to ensure the gear is secured on both sides, but that shouldn't be a big deal. (old 38 bracket on the right is coming off)
I should be able to use the stock cable bracket, cable, and kickdown once it's assembled.