hdv

What are the exact specifications you see when you import the format into AE and select the footage in in the project panel? You should see the height, width, pixel ratio, and sound settings.

What kind of camera was used? If the footage came from a Panasonic DVC PRO then the footage is probably 720 X 960 wtih a 1:33 PAR and it will perfectly fit in a 1280 X 720 comp. I would take that Panasonic HDV footage and put it in a standard (match the frame rate only) HD comp and use Fit Horizontal to scale it up and just work in HD. You'll be better off in the long run. As long as you don't monkey with the interpretation and you know the actual pixel dimensions you will not have any distortion. This advice comes from a guy that cut a ton of Panasonic DVC Pro HD 720 footage.  I never worked in nonsquare comp sizes, always square pixel equivalent. Come to think of it I also never worked in nonsquare DV Comps either. Nonsquare pixels were designed for cameras so that they could keep up with the available data rate and IMHO should never be used as a production format. 

Put it in a 1280x720 square-pixel comp.