I think the situation is this. The narrow frame will accept a K series up to 12hp. Over that, 14 or 16 hp, the frame is too narrow to accommodate the larger flywheel and shroud used on 14/16hp engines.. The 147/149 had the frame notched to accommodate the larger shroud.
If you take the flywheel and shroud from a 12hp engine and put it on the 14 or 16 hp, it would fit the NF without a notch.
I would not be concerned about cooling while blowing snow. (assuming it's naturally occurring snow, meaning ambient temps are chilly.) But cutting heavy grass in the summer might overtax the cooling capability of the smaller flywheel.
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