Andrew,
A chipmunk at 80" span would have about 7.5 square feet of wing and weight 11 to 12 lbs@ 25oz./sq ft. A 33 powerstroke would fly it fine, but a 45 or 46 would do better. CH has parts to convert to EI for both Poulan and Homelite. The extra power would be useful if the wing loading is higher.

Dave