You are asking for more than just motor combos.
Cut rolling resistance. This means a good front end aligned properly. Make sure the brakes aren't dragging, but will still stop.
ETs are power vs weight. Cut out weight wherever you can.
http://www.hotrod.com/projectbuild/1968_dodge_dart_wheels/index.html

http://www.moparmusclemagazine.com/howto/mopp_0609_1975_dodge_dart_sport/index.html

I couldn't find the one where they lightened up a later dart.

Get the engine to breathe. open up the intake and exhaust. Don't go too much, everything must work together.

A converter and gears will raise the RPM the engine works at, giving you more HP at a given vehicle speed. It will decrease MPG and limit top speed.