Without going inside the engine to get more pep around town and getting on the Freeway I'd go to 3;55 rear end, 700R4, headers, duel exhaust, and a small 4 bbl. Late 60s early 70s GMC 1/2 tons could be found with 3.55 Dana limited slip 44s. Don't go too big on the pipes 1 3/4" is plenty for the street. I run a 500 cfm Edlbrock on my 270. It's plenty. With the lower gear it will raise your rpms in the lower gears and make more power available where you want it. On the highway the OD will let you cruse 70-75 at around 2200-2500 RPMs depending on tire size.
