426 hemi in a 66 dart??????

Alterkation will defintly make it easier. Then you'll need:

Custom Headers
Big Block Tranny
Bigger Rearend
Bigger Radiator
Probably some inner fender Tweaking
Custom Driveshaft
Torque Converter
I'm missing a bunch, but that will give you a reason to start saving money and working overtime.

You should call Bill at Reilly Motorsports and talk w/ him about his front end.