I think this was resolved on b-pro for the most part, but I don't want to leave readers here hanging. The standalone MAF by GM can work even on a stock Bonneville, but you need to re-tune the car so that the MAF readings make sense. Once you get an external MAF sensor, you can go to any throttle body you'd like, any bore, any anything as long as the position sensor and idle air control can plug in. With the LS1 TB, there'* an adapter & wire kit so everything works.
Also, oldsman105 has an LS1 throttle body, but it'* on his 2001 SSEi on b-pro. I'm not sure if the pics are on this forum.
94 STEi and 99 SLO