Slant six with modifications runs horrible. What else can i do?

Blew My old slant six in my 75 dodge dart swinger a few years ago. Replaced engine with a freshly rebuilt one, rebuild trans, added a pair of offenhouser headers, exhaust, 2bbl manifold, 2bbl new 250cfm holley carb, msd ignition,etc. Idles rough and stalls frequently. Kinda slow right off the bat. Im looking to get more power out of it but keep it as my daily driver. Was put on the dyno last year with the bad trans a too big of a carb (500cfm) and had 201 ft lbs or tourque and 98 hp. What can i do to get her running well? Any advice is welcome. Thanks