welcome to FBBO from NorCal Sierras
Holley makes a
#4165 mec. sec. 650cfm #0-6210
or #4175 vac. 650cfm #0-9895
spread-bore dbbl pumper or vac. sec. carb too
they use to have larger cfm version, call them & ask them
1-866-464-6553
Chevy's used them,
IIRC, I think some were as big as 830-850cfm
on BB's mostly, some 350hp SBC & some (vettes) BBC's too
there's also the "new" Street Demon carbs
IIRC can be had in spread-bore replacements for
GM/Quadrajets or Chr./Thermoquads style baseplate
If an adapter is a height issue
but;
that doesn't look like a spread-bore/Themoquad
small primary & large secondary manifold
looks like a square bore, both bores are the same size