stock specs for 1963 292cu.in. truck engine was 165 hp but for low end torque and a really sweet sound (with split 6 headers and exhaust) its pretty hard to beat.
Some say you can bore up to .120 over but I wouldnt recomend over .060 for street. Throw in some offy or fenton add-ons and 2 or 3 carbs and you'll have a smooth power plant with a very sweet sound.
There are a lot of variations to building straight 6's have fun with it and keep us informed on your progress.