Carb Frankenstien Questions

ok so im looking for a 450cfm or so carb for a build were gonna do on my other dart... anyways i like holley's so im sticking with what i know, anyways...

im seeing a listing for the 9775 carb (tunnel ram carb i think)

http://www.ebay.com/itm/HOLLEY-DUAL...Parts_Accessories&hash=item19cffb14f1&vxp=mtr

is it possible to just buy another metering block and two accel pump float bowls to convert it to a normal double pumper?

or is the carb not drilled for it?

thx