i have something puzzling, this '58 cub i bought had a carb on it which was bad, by bad i mean it ran bad and leaked gas from everywhere, a kit did not help it, it still leaked, and would not run right , so i borrowed the carb off the broke down 48, temporary, the 58 now runs ok, i ordered a new carb for the 58, the only american one i could find online was a zenith, i have seen posts here where some didnt like the zenith, but cant remember why, now the puzzle, the carb will bolt on and hook up ok, but when its on, i cant check the oil, the dipstick is too large to pass the carb body, it is black topped, and is a larger part than the 48 has, so i went and got the small one off the 48, it wont work either as it wont seat on the filler hole on the 58's engine,the hole is too large, so i took the zenith off and just for grins took it out to the 48, for what it has, which is a smaller dipstick, and filler neck it looks like the zenith will work on it,whats happening here, i thought the 48 and the 58 were identical engines? have i got a aftermarket filler assembly, or could i have a much newer engine block in the 58 chassis? how can i tell?