Can you mod it and does anybody have one how do you like it

I don't know anyone but deadbird8 that ran one slightly modded carb and exhaust I think. I believe that I saw EVT may be able to mod them for ya,give them a call.

i just wont to know if i should go 36 briggs or 40 kolher

Briggs parts are more readily available. But yes you can mod the kohler. May be slightly more expensive, not sure.

From talking to several of the guys who do the mods, the kohler is a better built stronger block. Not saying for speed or anything else, just gonna hold together better. I know the case gasket problem on the briggs does not happen on the kohlers. The 27 kohler uses bigger bolts from the factory than the 35/36 briggs.

Having seen both motors I will say that the kohler was much more user friendly to work on. At the time the one that I saw needed a new coil and there was not a part shop in the country that could get it for me. I tried all the places that I knew locally and over the www. Also at that time they were going over some issues with them and not releasing anymore for marine service.