Claim of 25% HP bump true?

[Synchro909]

Originally Posted by Dodge

Rob Doe,

Yes, its done all the time. If your going to run a B carb you need either a B manifold
or a bored out Model A manifold. The B manifold sets the carb at a different angle but can be corrected with ovaling the holes in the manifold out or using smaller bolts.

Live and learn. I didn't know that. It might explain why my B carburettor cuts out when braking to a stop. The problem with a RHD car is the lug on the intake manifold for the ignition advance mechanism which is present on an A manifold but missing on a B because they supposedly had automatic advance in the distributor.
I am guessing here but does the change lower the intake or raise it. Details would be very welcome.