Yeah, that's what I had to do to convert a S2R800 internal fuel pump to external after the OE one failed. Drain tank, pull flange assembly from under tank, remove dead fuel pump, and cut off the nipple that feeds the fuel line. Now fuel drains to bottom of tank and out to external fuel pump.Biggest issue might be the fuel pick up.
Does the carby bike have an external fuel pump?
It's internal on the injected bikes so the pickup will not drain the tank like a carby one does, if they have an external fuel pump that is.
Might need to chop an internal fitting down.
Air box clearance might need checking.