Use an external pressure line instead.

To mod your intake to accept a big bore carb you need to use some JB weld to fill in all of the void holes in it (The pulse grove will be filled in).
Also you need to use a screw with a piece of plastic tube or spacer on it so that you can fill in the area as shown for the mounting . After you put on the epoxy use a razor blade to smear off the acsess. Then you have to drill out your carb & motor case and install a nipple in them so that the carb will work. Hope this helps. Tried to fing more pictures but this was all I could find.
Sammy