The 3.0 24V injector plates are 42mm ID. The bug QV runners are 45mm OD, same as the GTA runners. The 2.5 24V ones are smaller, maybe the same size as the 12V. That's why even on the Squadra tuning site it specifically mentions that anyone with a 156/166 2.5 24V who wants to install the 45mm QV runners need to get 3.0 injector plates. The runners are also smaller on the engine injector plate side, unless you get the 24V QV or GTA.
Not sure what size the GTV runners are, but the 164 Super 24V has small runners, but the injector plates are the same compared to the QV ones.
Maybe the engine you got had swapped injector plates and runners? Sometimes it's possible used engines get all the goodies swapped.
Sorry, didn't notice your post, yes it's entirely possible it already has all the 'goodies' - it was a part-finished project which was supposed to go in an Alfetta track car, but it looks like the project ground to a halt when the hybrid 75/164 oil pump proved to be an obstacle.