Sanguine: you'd be pushing it with 10:1 compression on todays fuel...unless you had a large enough cam to bleed it off it will probably detonate w/ 91 octane
383 man: Back in 1978 I built this 340 Dart Sport for my buddy. It was a 1970 340 I rebuilt to stock specs and did a nice 3 angle valve job with stock valves. No porting at all but I milled the heads to get a true 10.5 comp.
Thanks for providing more input. I've asked a question with lots of potential answers but I'm learning from the responses. It seems I might achieve the goal with a well built 68-70 factory spec 340, headers and the right drivetrain combo. One important question will be whether to build to the factory 10.5:1 compression ratio as it has to run on pump gas.
Moper, your reply helps clarify the machining issue. I've located a local machinist who apparently has extensive experience with race engines who should be able to do the job. I'll just have to see HOW expensive this will be (anyone have a rough idea what to expect?). I imagine this person will have a big influence on what I do but I'd like to be somewhat educated before I talk to him so this is helping. I've also ordered the Mopar performance secrets book.
Taking the advice to keep it simple, perhaps I can narrow this down a bit by asking, in addition to good machining and headers, is there an engine upgrade I would likely regret not doing during the rebuild?