here is what i came up with off these three. both of the FP manifolds do not have a perfect diameter on inlet or outlet - the west coast is almost perfect circle.
the inlet ports - if i have time i'll find a beaker and give you a volume diff in mL, but busy weekend - happy happy, joy joy.......:banghead:
inside ports -> the west coast looks to be same volume or just a little bigger then the 750 FP mani but maybe not quite as big as the 800. both FP mani's appear to be taller and not as wide and WC shorter, but wider.
my west coast is a little smaller them project ski @ inlet/outlet
height was measured using the bottom of center exaust port studs as a reference point - see pic
height - 74mm for west coast & 750-FP
71mm for 800-FP
Inlet @ Cylinder - 41mm WC , 41-42mm 750-FP, 40-41mm 800-FP
Outlet @ Head Pipe - 42mm WC, 42-43mm 750-FP, 46mm 800-FP
looks like you could easily take the outlet opening to 46mm without any problems.