330 to 350, 20 HP, 6%, not much of a change. We had the 330HP 3126 CAT in the Journey and at that weight, it was a ˜Hot Rod'. We have the 350 C7 CAT in the Horizon and with the extra weight, it's not the sporty coach the Journey was but it gets on down the road at close to 9 MPG, only slightly less than the Journey. I doubt an authorized CAT dealer would attempt to up-rate any 330 HP 3126 engine to 350 HP. If you have a C7, they may be able to get the factory to issue the authorization.
A factory authorized up-rate may very well cost you the price of lunch (1000 times over) since the factory would want to cover their potential warranty costs assuming that they wouldn't void any remaining warranty as a mater of course. I'll be quite curious to here what your dealer has to say about up-rating.
As far as I know, Freightliner has been using the same radiator for years and has just recently changed from a 1050 square inch to a 1000 square inch core. As you have probably read, several Cummins 400's have been having cooling problems with this radiator. I haven't yet heard of a CAT engine having problems and it's the same radiators for the 330 and the 350.
Have Fun!! Mark & Donalda 04 Horizon 40WD no TOW 90,900+ miles and counting
Triumph Bonneville & Susuki S40 on the back