My old pump gas 518 C.I. low deck pump gas stroker (10.29 to 1 comp. ratio)ran a best of 10.30 at 127.8 MPH through the 3.0 inch exhaust system with the Magnaflow 14x3 inch ovals muffs mounted at rear bumper with me in my 1971 Duster weighing 3450 lbs. with the six pack and air cleaner on the CNC ported Eddy RPM heads.
That motor on a DTS engine dyno in Ontario, CA with a .050 shorter stroke crank and 1.0 point less compression and a set of big valve mildly ported 906 heads made 612 HP @ 5500 RPM and 644 Ft. Lbs. at 4500 RPM
I was really happy with that motor and the results it would produce with the changes I made on it, the last combination was a set of Indy SR M.W. heads and a Indy 400-3 intake and a holley 9375 non HP carb made 727 HP at 4300 ft in Klamath Falls OR. at 4300 ft. altitude. That was the last changes I made on that car and it made the car run 9.993 at 134.7 MPH through the full exhaust and on 91 octane OR non ethanol pump swill at Woodburn in late summer
You can made decent power with the standard port heads on a BB Mopar
Better heads will make more power also with no other changes
Now, how fast do you want to go