Another consideration to go along with the one mentioned by Josiah - how is the intake manifold modified to use the two-barrel. The one barrel to two barrel adapters typically cause idle and low end issues.

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