if I was replacing the original 6 cylinder on a 1971 duster what would be my best streetable option ?

Demon and Duster first two cars I owned. Loved them. What are you wanting to do with car? Upgrade to larger motor or restore back to its original glory?

defiantly looking to add a small block, ( forgive my ignorance I have built nothing but Chevy's ) I am assuming you just change motor and transmission mounts to add a small block and bigger trans ? also would you need larger front springs ? I am not sure what motor is best for performance 340 or 360 ? or parts availability ? I am also assuming the heads are interchangeable ? the reason for all the questions is a neighbor has a nice looking 1971 Duster with rally wheels sporting a 6 cylinder, this economy has wiped me out so I thought I could buy it now for little and add the new running gear down the road if it is that simple thank you for your time Drew

I am the wrong one to be talking to if you doing that. That one has the original slant six in it if I am not mistaken. If mine I would not change it out. That motor will outlast anything that you could ever put in it. Sorry but I just one of those guys who likes to keep old cars as they were new. Although I have seen some with modified intakes to hold duel carbs, modified exhaust, and even one with a turbo modified to it. So there are some neat things that can be done to that tough little motor.

http://www.jalopyjournal.com/forum/showthread.php? t=266175&showall=1

Had not looked into these motors in years. But it seems there is a lot more you can do with them than I had mentioned. Consider building your slant six. I don't think you will be disappointed when someone peaks off under your hood and says "damn look what you have done to that slant six"

Thanks Mark That certainly changed my thinking, a lot less work better gas milage and can still have fun, not a bad deal. Thank you

Thanks glad I could help. There are so many neat things you can do and have a one of a kind when you are done. Remember to keep us informed on your progress and post some pics of her in your garage. Drive safe.