The best method is to go to your local shop/tech and have somebody measure your frets with calipers. Fender tends to use vague terms like "medium" or "medium jumbo" but if you're ordering a neck then you'll want to have the Dunlop or Jescar fretwire number. Here's a chart: http://www.lutherie.net/fret.chart.html
If you like the feel of shorter frets, mandolin frets are fantastic but smaller frets means you can only level them once or twice before they need replacing (that may or may not be an issue depending on how your playing style wears on frets).
A word of advice: whichever size you choose, go with stainless steel or EVO fretwire as they last much longer than standard nickel silver.