4bbl

I too have run a stock internal 225 with Clifford headers, Intake,390 Holley,split 2 1/2'' pipes from the shorty headers Y'ed into 2 1/2'' single exhaust,Flowmaster 40 muffler and a 2 1/2'' tail pipe. 2.94 rear gears. Later went to a 500 Edelbrock when the 390 started to act up. Edelbrock worked better over all.
This is just my application,,,Your results may vary.....