Mike:
There's many studies that show positive effects of strength training on endurance.
Of course, diet needs to be programmed to ensure that there is no loss of body mass, AND the strength training MUST be programmed along with concurrent endurance work so that endurance adaptations are not lost.
There is a reason why elite endurance runners and such do have power/strength work in their training.
http://www.ncbi.nlm.nih.gov/pubmed/18545191
http://www.ncbi.nlm.nih.gov/pubmed/19816215
http://www.ncbi.nlm.nih.gov/pubmed/18978605
http://www.ncbi.nlm.nih.gov/pubmed/19077735
etc.