of Carbs and Transmissions

I put a new Edelbrock carb on the Caddy's 429.

a. It's AMAZING what happens when the fuel goes IN the motor, vs running out all over the TOP of the motor.
2. I'm just not used to the motivation a 429 can have on 6000 lbs of Hearse. Stuff I had up on the dash actually flew back off onto the floor.
III. It made the exhaust leaks MUCH more noticeable. It now sounds like a chariot of the damned.

Problem being, I thought it used Carb vacuum to modulate kick-down, as there was a hard line going from the tranny to the old carb. The new carb's connections are about 2" further forward, and I cobbled together an extension.

I then referred to the Factory service manual and determined that the transmission uses two switches, to be actuated at 30% and 60% throttle to request downshifts.

I see that there's a tab on the throttle assembly to most likely take a NOS switch, but that's not exactly going to provide what I need. I was wondering if anyone else has dealt with this particular issue before? If not, it may be a good excuse to play what that new rotary table I picked up from harbor freight and make a cam to do so.