Slant 6 A Body advice. Engine and chassis.

I have a few questions and I am looking for advice and maybe some tips from people that may have built what I am trying build.
I have a 1972 Duster, slant 6 3 speed manual trans with a 323 rear diff.
I want to make this car more practical and fun to drive.
I have already switched it to factory Mopar electronic ignition with and Orange spark box. The car has manual brakes and power steering.
Questions.....
I dont want to make a "hot rod" just a better motor. So I want it to breathe better is there some head work that can be done to improve intake and exhaust flow? If so what should be improved? porting? changing valves? I want this to be fun and keep it on a budget, thats part of the fun.
In the end I want to keep the base engine intact. No cam change and such. I have an extra cylinder head what mods should be made. I would also like to run a single one piece header and a multiple carb intake. maybe 3 1 bbl or 2 2 bbl carbs. Good or bad idea?
I would also like to change the trans to a 3 speed with an overdrive. This seems to end up turning into a can of worms. So with this question I hope to hear from some one that has done this swap so I know what to look for at the swap meets.
I want to loose the power steering, Its too "easy" and no road feel. What is recommended for a manual gear?
Suspension, I am going to lower the car front and rear Blocks in the rear and tun the torsion bars a bit! The car has no sway bars. Looking for recommendations on size and brand names.
This is a fun budget project using craigslist e-bay and swap meets. Any advice would be great!