[unruhjonny]

that book is wrong.

the "late" 1968 Ram Air IS the round port RAII;
L67 is the regular production order code for the Ram Air engines - and when the D-port Ram Air engine was replaced, the round-port Ram Air engine WAS the only Ram Air engine.

It is well known that for 1967 that the Firebird Ram Air Quadrajets had tabs on the throttle body which limited the ability to go wide open;
If the throttle bodies were different, then it makes sense to do different application numbers between Firebird 400 and GTO - except in 1968 the tabs were no longer there - my guess is that PMD intended to have the tabs present on the 1968 Quadrajets, but didn't.
For the RAI there are four application numbers of Quadrajets, and interestingly, they all had one service replacement application number (this serves to suggest that PMD knew that the Firebird 400 & GTO Quadrajets were the same thing). That service replacement was a number previously for a Firebird 400 - 7028276. (I am surprised that the guide makes no mention of this.)
The different Firebird 400 vs GTO carburetor application numbers simply went away with the "late" Ram Air engine - both body styles used the same application numbers.

I believe (don't have literature handy) that the 1968 applications of the 7028270/7028273 also used the 7028276 SR carb;
I believe that the 1969 applications of the 7028270/7028273 used the 7029270 as the SR carb.

I had understood that 1967 & some 1968 Quadrajets had issues with the quality of the casting on the fuel bowl, which was the reason so few of those original carburetors exist today.

Additionally, that book doesn't list the two casting numbers of intake manifolds used in 1968;
I believe (going off memory here) the change over was somewhere just before the introduction of the RAII.
All RAII engines should have the later casting intake manifold.
'early' intake manifold: 9790140
'late' intake manifold: 9794234

The late intake manifold had the same size runners as the prior D-port engines, and was NOT the taller runners that the RAIV & 455HO/SD455 used.

For a brief time, my cousin had what may have been the very latest built RAI Firebird; it had the later intake manifold casting number.