BAN ONE is the polishing expert here. He's even polished his windshield wiper motors on his car. (NO, I'm NOT making that up!) Get in touch with him and ask him about what he does -- he'd know if anybody would.
The "tri-power" intake systems were used on the early GTOs and as Hammer said consisted of 3 2-barrel carbs linked together. They were never used on Firebirds (even gen 1s) from the factory, although I'm sure somebody has put such a system together. Basically when GM went the spreadbore Q-jet they found they had no need for the tri-power setup -- so it was dropped.
The Ram Air engines of the early 70s (which morphed into the HO and SD engines) were the result of a lot of development work by Pontiac. These engines had vastly improved flow rates compared to the mid-60s to late-60s engines. You'll want 70s hardware for your gen 2 Firebird, just be sure (as Hammer cautions) that you don't try to mix round port stuff with D port stuff. As far as pricing for what you have in hand, acertain what it is -- HO stuff goes for more than standard, and SD stuff commands an even better price, and the standard "log" manifolds used on regular 455s (non-HO/non-SD) don't sell for much.