I'll weld it on (badly)
the SR t/b has a different footprint paul (and a remote i/c/v i believe)
The ga15 is exactly the same as the ga14/16 but in the same body as the cg10/13 if you know what I mean
to tell ya the truth i don't know if a bigger throttle body will make any difference without cams ect on a turbo job i could be wrong but seriously will it give any more poke?
I doubt you'd get much extra tbh, as you're running forced more air is getting in and occupying the same space anyway. Inlet manifold will have a smaller restriction again after the TB (one reason i was thinking about making a different one, but never did).
I guess it'll come down to experimentation.