3in exhaust vs 2 1/2 in?

Iv got a 65 GT.Its got a 302 .040,speed pro hyp.flat top coated skirt pistons,total seal gapless rings,ARP studs,double roller timing chain,comp cam 280H hyd. flat tappet cam(280/512), 351W heads with over size valves,double valve springs,weiand Xcelereator intake(waiting to go on),Holley 670 Street avenger carb(waitning to go on),Mallory Unilite distributor,Mallory Promaster coil,stock C4,stock rear.I plan on changing the tranny to an AOD and swaping the rear for a 8.8 or 9 with 3.73's, locker,coil springs,and disc brakes.I work at an exhaust shop so I plan on bending all the pipes myslef instead of buying some mandrel bent stuff.I dont know wether I should go with a 3 in exhaust with H-pipe to 2 3in in 3 in out mufflers and 3in tail pipes out the back or go with a 2 1/2 setup.What would be the pros and cons of each.Iv heard very few 3in setups but the did sound good. Im eventually gonna replace the motor with a stroked 351w with a suprecharger or turbo.
 
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