Grasshopper 721 vs Grasshopper 725

I am looking for information on my 2001 721 Grasshopper, particularly the carburetion of the Kubota engine. I have always noticed that the 721 and the 725 have all the same specifications including the displacement, the boar and stroke as well as the test RPM. It would appear that the only possible difference is the carburetion. I do know for a fact that Briggs & Stratton did this exact same thing between the 12.5 H.P. on the Grasshopper 612 and the 14 H.P. on the 614 with the only difference being the carburetor. I had a dealer sell me a carburetor for a 614 and installed it on my 612 it gave me a noticeable increase in H.P. enough extra power to run a blower/bagger on my 612. In any event if I can boost power by 4 H.P. for the cost of a carburetor it would be worth it, I have gone through the parts manual and it also appears that the parts breakdown between the 721 and the 721 are identical. Can anyone confirm my carburetion theory?

I am also interested in this topic as well. I have heard the same thing about my Kolher Command 20HP and the 25HP. Boy would it be nice to get another 5HP. If anyone has any information on this it would be appreciated.

Just found this forum and I realize this is an older thread but the manual (form 172206) for my 1996 725 is also for the 721. It states that the 721's Kubota gas engine is a WG600-B and is 600cc (36.61 ci) displacement and my 725's Kubota gas engine is a model WG750-B with 740cc (45.2 ci) displacement. I'm no expert, just relaying what I have found FWIW.

Interesting as far as the specs. for the 1996 models, the 2001 Kubota manual that come with the 721 clearly shows them the same line for line.

Sure would like to pick up them 4 horses!