IF Sizing
It would depend on if the bike has some odd dimensions. IF's are mostly made-to-measure. Back when they did offer a "standard" size option they were very similar to Lemond geometry. I would try to take a tape measure to the frame. Measure from a spot in the center of where two tunes meet to the appropriate opposite joint. If the top tube is not level, try to estimate level, unless the frame has fork, headset and wheels attached... Your leg, torso and arm-length measurements would help determine more closely (as well as a fexibility assessment), but a 54 or 55 with reasonably normal top-tube, head-tube lengths and head and seat tube angles will probably work pretty well fro you. Once you take the plunge into a road bike, have someone EXPERIENCED work with you to get your riding position right. Don't hesitate to pay good money for this, it will mean the difference between learning to love road riding and thinking we're all nuts on the pavement...
Bob