Putting a 426 Hemi in a 1966 Barracuda

I've found a '65 Barracuda, which my wife has fallen in love with. I've always wanted to put a Hemi in the car that I buy (boyhood dreams never die, right?). I don't know how easy it would be to switch the slant 6 out and put my Hemi in its place...or if it is even possible? Thanks for any help. Really glad I've found this site!

ADD-ON-
If this is too hard to be a realistic goal, would an early to mid 70s Duster be an easier install? Or just as difficult? Again, thanks for all your info and help!

FINAL ADD-ON (I hope)

The car will be for street driving, so I need to be able to fit defroster motor, wipers, etc. back in bay with the Hemi? Thanks again!
The 67 and later A bodies like the Duster you mentioned would be a much easier conversion. Nothing about a Hemi swap will be cheap though. We talking 426 Hemi or a late model style out if a newer car. Probably doesn't matter but just curious?