Small block rebuild

Hey I’ve got a ‘73 scamp 225 /6 and was wondering what motor I should go with need a deep low rumble in the back. Would like some extra horseage but keeping it stock...oh and what are these cars more? A valiant? a dart? a duster?? Values and other knowledge is encouraged to pass down!

or just leave the slant in there forever and everr

Here's what you do
Cut the muffler off a exhaust pipe and pull the number 3 spark plug loose.... theres your "rumble out back"