First things first. Tune the 273 up. Start by adjusting the valves, they should be solids. Make sure the passenger side exhaust flapper valve is working or at least open. Set the timing to 10 degrees BTDC. I'd rebuild the 2 barrel carb to keep you running till you get all the parts to make that 273 a performance engine. Your heads are good as is your compression, almost 9:1. Are you running an automatic transmission? I have to agree on starting with a quick curve distributor, and would suggest
@halifaxhops. The 4 barrel swap is more involved and a number of changes have to be made at the same time. Do you know what has done to your engine?
The best thing you can do for exhaust is use the 67 Barracuda Commando exhaust. It uses your factory exhaust manifolds, the y pipe empties into a 2.50 OD pipe and runs to a muffler with a 2 1/4 tail pipe. The 2 1/4 tailpipe uses the standard HP pipe hanger. It will work very well no matter what mods you make in the future. The complete system is about $550 from Waldron's Exhaust and is a copy of the original 4 barrel system minus the resonator.
[URL]https://waldronexhaust.com/pro...uda-v8-273ci-4-bbl-carburetor-single-exhaust/[/URL]
The earlier system was straight thru muffler and resonator included. In the mean time you could run a straight thru glass pack like a Cherry Bomb on the 2 barrel exhaust system.
[URL]https://cherrybomb.com/cherry-bomb-glasspack/[/URL]