opinions on a 340 build

for "commuter" you need to think 3 things:
1. comp ratio.... between 9 and 10:1 not more not less. more will detonate on street gas less will get poor mileage. 500c.i vs 416 dont matter. it's the ratio that determines how efficiently the gas/air mixture is burned. SUPER gas from an exxon not from a convenience store. if you want to run bad gas 8:1 comp ratio.

2. manual shift. 904/727 auto trans with converters are very poor you lose about 30% wasted on the non-lockup converter. i had a 340 dart with a 4 speed manual trans i got 19mpg

3. weight. less weight = better mileage. aluminum heads & intake are better than iron. lighter wheels and rubber save gas. dont get 19" wheels and mudbog size tires and expect to improve your mileage or braking. big huge rubber absorbs a lot more torque to get it spinning (more braking to slow it down). spinning weight is even worse than extra non moving weight in ruining your mileage.

as far as stroker kits please please read this article before you buy one. ... you have to be very careful as some of them come from the factory improperly machined, and many people have had bad luck just putting them in their engine right out of the box...

http://www.musclemotorsracing.com/muscle-mike-blog/122-stroker-kits-101.html