Any gains adding 1.6 rockers to stock 273?

I'd skip the 1.6 aftermarket rockers. You already have a bullet proof setup with the 67 solid lifter rocker system. We played with a 273 2 barrel engine for years as a test mule in my brothers 67 automatic trans Barracuda. Spend your money where it will give the best bang. Start with at least 3.23 gears in the rear. Second, get a 4 barrel intake and carb, anything from an original HP 273 and AFB to a Weiand intake and a good 340 TQ. 1967 DODGE DART Weiand 8007WND Weiand Action Plus Intake Manifolds | Summit Racing Third, change trans fluid and filter, get a 4.2 kick down lever BAND LEVER - A&A Transmissions , adjust the bands and bump up the pressure, add a part throttle kick down module 727 3-2 Kick Down Module (1966-69) - A&A Transmissions, get a 340 kick down linkage or a cable kick down system. Swap exhaust mufflers or get the 67 273 Charger 2.5 single exhaust 1965-66 Dodge Dart GT w/273 4 BBL Single Exhaust w/Resonator Eliminator Pipe or A-Body HiPo Exhaust System-(See option menu for applications . Last, get a cam for your car by talking honestly to a cam manufacturer, lifters, valve springs, and a double roller timing set. No problem using the stock heads or short block. 2 barrel pistons are usually around .020 below the deck and you should have closed chamber heads.