Alan Couzens, MS (Sports Science)
You'll find below a calculator that will give you an equivalent bike power (in watts) for a given running pace.
To use it, simply enter your weight (in lbs) in the first white cell then a given (flat) run pace (in the format h:m:ss) in the cell below. E.g. for 8:30/mi, enter "0:8:30". It will the spit out an equivalent energy output (in watts) on the bike.
A key element in my "energy pacing your ironman" pacing strategy (here and here) is that you negative split the race, i.e. that you're putting out more 'power' in the run portion of the race than you are for the bike portion. This calculator is particularly useful as a 'check in' on how well you accomplished this (or whether you left some time out there on the course).
Ideally, your "run power" should just about always be greater that your normalized power on the bike for any 70.3 or Ironman event.
This calculator is based on average economy numbers of 75W/L on the bike and 210ml/kg/km on the run. Actual equivalencies may vary a little with specific economy differences but this represents a good 'ball park' based on the average of triathletes that I have tested in the lab.
Hopefully, you find it useful & it can help to lead you to a PR in 2014.