I'd never run two Holley carbs in line, and I'd damn sure never use a vacuum secondary carb on any TR.
The benefit to the Holley style carbs is the dual feed, one to each bowl. Rather than one line feeding two needle and seats, you have one line feeding each needle and seat.
The other thing is the bowls are outside of the main body so the fuel stays cooler on the Holley than the Carter style carb.
Your combo should have two 750's on it, sideways. Make sure you get the slant cut floats so when you drop the hammer and the fuel moves to the back of the bowls it doesn't lift the float and shut off the fuel.
The linkage isn't really an issue. It's an added expense but it's really simple.
If you are not going to turn the Holley sideways, fix what you have.
