I doubt you will find a commercial generator that perfectly lines up with the existing mounting holes, but stranger things have happened.
What commercial generator are you talking about?
You're asking such a generic question that it's impossible to give a good answer to it.
You have 43" between the fenders to work with and 5k lb rated load for military, but probably double that for civilian use.
There are lots of different commercial and industrial generators out there, so as long as you use one that is the right size it will fit...
You can pretty easily fit a Cummins Onan 5kw commercial diesel as it's only 400 lbs and 34" long x 23 wide. You could easily fit 3 or 4 of them; more if you make a frame to raise them above the fenders. Only 400 lbs so you could easily do 10 of them and a 100 gallon fuel tank and still be under the military rating.
On the upper end, without doing anything to raise the generator above the fenders, there are 100kw units out there weighing less than 5k lbs, and 40" wide. I'm sure you could find even larger ones than that if you looked longer. Can easily go wider also by raising it up above the fenders.
