Flowmasters too LOUDDDD..& Cuda Duals...
If the 273 is a Hi-Po motor (4bbl) don't crap it up with duals, put the factory 2.5 inch pipes back on it with the oe small flow through muffler and the oe rear resonator with the chrome exhaust tip attached. It breathes real nice and produces a great sound, the only issue is its a bit pricey - $750.00 for the complete system Y-Pipe back. You can check it out at Accurate LTD Exhaust systems at
www.accurateltd.com enter the site and click the tab at the top right "complete systems" then go to A-bodies. I have a 67 Hi-po that somebody (long ago) put a 1 7/8 system on thats now rotted out (I'm saving my pennies) I did hear the OE system and it sounds pretty good.