Just took a quick look at the pictures and it seems that the units are Holley 2 bbl bolt patterns, not Rochester. There would be a lot of adaption and fabrication to make it work on a Rochester based manifold.
I believe that Fitech made their units to fit Mopar and Ford manifolds mostly, and perhaps the chevy 427 tripower unit, which I believe also used Holley carbs. Adapting them to a Pontiac intake would be difficult, but it probably could be done by someone intent on using these throttle body units in place of carburetors.
There are adapter plates to adapt a Holley baseplate to a Rochester manifold, but no one knows until you try it if there is enough spacing room between units to mount 3 of them in a row.......
It could be a costly endeavor to make them fit if the adapters have to be offset to make enough room for everything to fit.
The question you have to ask, is the juice, worth the squeeze? It probably wouldn't be high on my priority list to make my tri power setup fuel injected, considering all the headaches you may run into. But then again it may all bolt together without any special adapters. One other problem I can foresee, might be an air cleaner, as the Rochester single units won't fit a Holley top pattern.
I guess it boils down to, how badly you want a FI tri power setup?