Your manifold is a "B" type - a later four barrel version so you have as good a factory part as you will find.
This photo shows a way you can make the adapter and heat isolation spacer the same part. The 1/2 inch phenolic isolator is available from both Speedway Motors and Moroso - maybe others as well. It matches the 1.438 Ford manifold bores exactly on the bottom (thats the way it comes). By matching the upper side of the plate to a carb base gasket, it does both tasks at the same time. The phenolic material is easily filed and sanded to a smooth transition - a funnel that smoothly transitions into the manifold bores. You don't want any sharp edges in the air stream below the base plate of the carb. Be sure you don't taper off too sharply, use the whole half inch - as the butterflies turn beneath the base of the carb they can "re-seat" on the spacer and alter air flow more than you expect.
A "closed " four hole spacer that keeps the two sides of the 180° manifold seperate will help build torque and these Y motors are torque motors.