66 barracuda modern v6 swap?
I asked the same question about a year ago I think.
I think most of the responses said something like, "if your going to bother doing a swap, why not just do a v8". They all said the v6's were low on power and didn't really get any better mileage than say a 5.2 magnum (with the factory fuel injection still on it).
I always thought it would be a cool idea, a little different than what everyone else is doing.
Here's some info from allpar that might help you.
http://www.allpar.com/mopar/39.html