The 248 would have originally had some form of Zenith. As Zenith used the same physical size for different internal sizes (CFM ratings); it may be possible to find a Zenith that will fit the original intake with a larger venturi. Zenith 28 size 11 carbs can be had with CFM ratings from about 170 to 220, depending on which venturi is used.

Jon.


Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
If you truly believe "one size fits all," try walking a mile in your spouse's shoes!
The Carburetor Shop