In reply to philhilo:
The biggest way running will impact on your climbing is when you start doing more running than actual climbing!
I started running to get fitter for climbing then entered a race, then another race, then I had to train for the next race before I knew it I was running far more than I was climbing.
I pretty much run 4 days a week and climb once every fortnight if I'm lucky!
I know this isn't exactly that answer you were looking for but heed it as a warning- Running can become addictive!
Dave D.