3/4 drill or hole saw?

Don't know if this will help any.

Quote from http://www.slantsix.org/articles/dibiase_efi/efi-conversion.htm.

I've been told that the Clifford manifold would be best for converting to fuel injection because it is supposed to have better flow characteristics and already has the injector bosses cast into it. However, this manifold must be used with headers and that's something I didn't want to do. It is my understanding that headers are not the best choice for a turbo setup, which is my ultimate goal. Based on this, and the cost, I chose the aluminum Offenhauser 4-BBL manifold. This manifold is still available from JC Whitney (www.jcwhitney.com) as P/N 73ZX7653A for $230 (wrong picture on web site), and Performance Automotive Warehouse (www.pawinc.com) as P/N 5720. Of course, the least expensive alternative is to use your stock cast iron manifold, or even the stock aluminum manifold. For my setup I had Rance Fuel Injection (www.rancefi.com) do the machine work and weld the injector bungs and fuel rail brackets on my Offenhouser manifold. The total cost for the machining, welding, and the fabrication of the fuel rail was $460. Rance is also an Accel and Offenhauser distributor.