Yeah GT"3040" means GT30 turbine with GT40 82mm compressor wheel . These were originally an older HKS spec turbo and the difference between theirs and the Garrett marketed version was the compressor trim - 50T vs 56T . You basically got a bit more airflow than a GT3037/GT3076R 56T with the 50T 3040R . Even when HKS went to a cropped GT35 turbine in their GT"3240R" they kept the 82mm compressor trim at 54 .
And yep I reckon a larger turbine housing on the original turbo would have been the simple and cost effective option . From Garretts maps you get a healthy flow increase with the GT30 turbine going from 0.82 to 1.06 turbine housings , logical step with an RB30 in mind .
If the ask was 330+ I reckon the way to keep the turbo responsive is to increase the housing size because the rotating groups inertia doesn't increase like it will with larger wheels particularly the turbine . Garrett already gives you a 0.70 AR compressor housing on those "7 blade" GT3076Rs so changing turbine housings if required is straightforward .
One further , I'm not so sure the 7 blade wheel is a T04S . From memory their blades have a leading tip if you know what I mean where the S and 60-1 series had perpendicular blades . The 7 blade one could be TB41 series but whatever . GTX is the foreseeable future .