Need help tuning a 273.

This winter i switched out the slant 6 to a 273 in my Duster. The 273 was previously owned by a friend of mine and ran really good in his Dart, strong and quick little engine.

I haven’t really done anything to the engine besides cleaning and panting it, changed filters, oil etc. I had to remove the carb and distributer when we pulled the engine, so that and the headers is pretty much the only thing that’s been removed and put back.

It does run now and idles fine, but it is nowhere near as strong, quick or alert as it was in the Dart last summer. It has a stumble and hesitation if you stomp it when idling and taking off. If I am in neutral and rev it, it feels somewhat alert, but from idling it kinda feels like it’s not running on all cylinders. I pulled each wire though and it does run on all.

It has headers a 4 bbl edelbrock and the previous owner said it had a somewhat ”wilder” cam.

I hope it is a tuning issue. Any suggestions on how to start tuning it? I used the coil from my old slant six, could that be an issue? How would you set the timing? I don’t have that much experience so please help out if you have advice.