Wondering what upgrade would yield more HP gain, roller rockers or 2.5" exhaust system (with or without X-pipe).

Have: stock stamped rockers, 2" dual exhaust thru mufflers

Car: 71 Challenger w/318 recently stroked with 4" crank. Performer heads, MP hydraulic 474/280 cam, air-gap intake, 750 Performer carb, Summit headers, 10:1 CR, 727 TF. Used mostly as cruiser (3.23 gears, 2500 stall) but like to run occasionally at strip. Usually shift around 5K, still pulling hard, 12.95 ET.

Like the torque monster, but wouldn't mind a little more HP. Heard the rockers yield anywhere from 10-25 HP over stock, have no idea what the exhaust would do. Love to hear other's experience.

Thanks in advance.