You are better off sticking with the EFI, its a great system.
If you do switch to carbs, I suggest dual SUs from a 240.
Reason is the SUs are a sidedraft design, just like the motor.
4 barrels are a downdraft design, built for downdraft V6s and V8s
Not saying the 4 barrel wont work, but it sounds like you want more performance, and SUs are the way to go vs the 4 barrel for top performance.
A new 4 barrel intake will cost about $300, new carbs vary depending on what you want. A complete SU set with everything you need is $1000 for like new parts from Ztherapy, I own a set, and they are a high quality design.
Also remember, when you change from EFI to carburation, you ned to change your fuel pump and pressure regulator. You will also have to rewire your fuel pump because it is controlled by the EFI.
P.S. Just in case you are wondering, I had a 4 barrel on my 78 Z, and I got rid of that for SUs and I will never go back.
In case this helps a single stock SU carb can flow a maximum of 152 cfm...
I just switched to the 2 inch HS8 SU carbs... bought them from a dealer in the UK... Sorry they were the last set he had, but based on my calcs a 2.8 should do fine with SU's all the way up to 7100 rpms.
My motor is a 3.1 stroker and the stock SU's couldn't keep up, thus I moved to the larger 2 inch carbs... made a huge difference.