the correct carb size for a 273 is 500 cfm,,you dont want any thing bigger on your 273 weather it has the hipo cam or not,,500 cfm is enough[/qoute]
In my research I was led to believe that the 273 Commando came with a 550cfm Carter AFB as Original Equipment and Single Exhaust
the 273s came with 500 cfm,,and the factory D DART race car came with a 600 holly,but much bigger cam and rear gearing,,, 500 cfm is plenty,,and an AVS would also help as to not open fully untill the engine needed it using an auto matic,,,much crisper responce at low end cruising
And it is also Believed that the 1966 "D Dart" came with a 750cfm Holley carb and Aluminum Intake, Exiting through Headers by DOUG
I have a 67 Dart GT 273 4Barrel with a Holley 600cfm and Dual exhaust with stock manifolds and Cam. (some mild to aggressive machine work including porting Milling and Boring) It needs an adapter plate to fit. I am looking into a Dual Cold-Air style Cleaner for more crisper fresher air for my 273.
3:91 gears and a 4-speed keep it revved up...