yup !, just when you thought it was safe and you had it figured out, surprise?
pretty sure your machine was the only one built with the prototype pontoons,
now what is interesting, i have the twin 422 to yours 148055, last '48 built, and it came with stamped tucker pontoons, this is confirmed by a factory photo, and then, and the next was 149056, a trailer, next, 149057, is the torpedo that we just hauled home, and it came with the flat side with a single crease down the side of the pontoon, again, factory photo shows this pontoon.
so, yours having the outlined stamped pontoon - prototype - is most interesting, does show tucker never wasted a single part and built no two sno-cats quite the same. these 3 sno-cats, all built together at the same time, sequential serial numbered, each, with a different pontoon style
and the more you learn the less you know.