Max pipe diameter for a 318?

I am happy with my setup.

I am using, step up from stock 1 7/8" (1964 Abody manifold)
up to 2 1/4" thru Dynomax Super Turbo mufflers.

Edelbrock 600 cfm, # 1406 carb
Edlebrock LD4B intake.

Mopar Performance cam, .435/ .450 lift part #4452759

Basic Operating RPM Range: 1,200-5,200 RPM
Intake Duration at 050 inch Lift: 221
Exhaust Duration at 050 inch Lift: 228
Duration at 050 inch Lift: 221 int./228 exh.
Advertised Intake Duration: 260
Advertised Exhaust Duration: 268
Advertised Duration: 260 int./268 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.430 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.450 in.
Valve Lift with Factory Rocker Arm Ratio: 0.430 int./0.450 exh. lift
Lobe Separation (degrees): 110

I also have # 302 casting heads. :)