Howdy Gumpn2:
There are two options to mount a 2 barrel on a US head. One is to buy/make an adaptor. Adaptors are available from Cliffords and TransDapt. The down side of an adapter is less hood clearance and less than full benefit from the capicity of the larger CFM two barrel.
The second option is to mill the original 1 barrel carb pad off the log, enlarge and oval the new hole and make an adapter to fasten to the modified log and with studs to mount the carb on top of it. I think Geezer has some pictures of this process on his site. This method gets max performance from the 2V and actually increases hood clearance.
The two types of 2 barrel are the Holley/Weber 2 stage two barrels and wide base Holley 2300 and Autolite 2100 2 barrels. Each has its advantages and short comings. All are a significant improvement over a stock one barrel.
Adios, David
