6/carbs: ? about tall 2ndary venturi's, rich, I miss you. Options

[brant]

carbs: ? about tall 2ndary venturi's
Hi all... thanks for the help in advance.

I want to try a set of the tall 2ndary's on my IDS-3C carbs.
I'm running the stock ones and want to try the tall ones, that I've heard called "906-style"

its a race car and withoug re-hashing all of my jetting and dyno history, my questions are:

1) pierce manifold says they have 2 different types in stock a 3.5 size and a 4.5 size. I believe this measurement is in reference to bore and not height. Pierce said that both sizes are the "tall" type. Which do I want? Motor is a 1967 2.0/S motor at altitude.
(the pierce catalogue references that the IDS carbs came with 4.5 short, but I'd like confirmation before I order)

2) Does anyone know if these tall secondaries interchange on the IDA carb versus the IDS carb. I would assume so, but I once bought some F33 emulsion tubes from Pierce that do fit the IDA, and found that they would not fit the IDS. I didn't know there was that much difference between the two carbs, which surprised me. But again, before I order do people know if the 906-type tall 2ndaries will fit an IDS-3C body?

again, thanks in advance everyone!
brant