360 la headers & straight pipe

A stock 1973 360 is very low compression (barely 8:1) and if it has a 2-bbl cam it'll hardly make any noise even with open headers. My '72 D200 has a 360 with stock 2-bbl cam and when I put headers on it I drove it around for a bit with no exhaust and it was only loud when I revved it or had it under load.

At bare minimum you need to put some sort of small aftermarket cam in it to get any decent sound. You will probably need mufflers after that point too lol. I will likely put the smallest of the Lunati Voodoo series hydraulic in mine to keep the bottom-end grunt but since yours is in an A-body the second smallest one should work well. It'll give quite a power boost too, stock non-HP cams are a joke unless you're lugging the engine at 1000 RPM all the time with a manual transmission in a big heavy truck.