400 bbls engines were the only ones with stock manifold to spreadbore carbs

as stated 383 intakes will work but not 440s but once again stock 383 never did come with spreadbores setups

another good option is get a 2186 performer Eddelbrock intake what is practically a copy of the stock 400 4bbls manifold ( althought does have the 383 numbers casted )

I already got an used 2186 eddy intake to my 400 that I will mill the 383 numbers and paint on engine color to keep stock appearence. I know won't be a BIG gain over the stock one, but still will be a plus being cooler to keep safe the carb and lighter...then easier to port too.