If you call sumit, they can answer your questions better than I can. As for heads, Summit sells Vortec heads cheep, may be cheaper than doing a performance up grade to your heads. I have thought about a cam up grade on my truck for a long time, but haven't done anything yet in fear of the high milage I have, and the engine not holding up. As for as lopeing, computer cams tend to not lope near as much as a carb engine. Also performance heads will have help improve the effects of a cam up grade. A cam, and head swap that is tuned to work together is the best way to go. On a carbed 350, a port and polished head swap with a 292 cam will make some grate H.P ? An engine is just a big air compressor. The more air, fuel you take in, and get out of the engine, the more power it will make, but keep in mind, performance and gas mileage do not work together when you are talking H.P. the stock Vortec fuel system is good to around 400 H.P. or so I hear. A cam, head swap, with a good tune, a free flowing exhaust system, and cold air filter, should get you close to that. From my past research, a 262 cam, looks to be a good choice. Port and polished heads with screw in rocker stud bolts are a good option. And there are some limitations on how far the valves can open on stock Vortec heads. This can be cut down to alow for a lerger cam.
