Board x height

Question
For someone 6 foot tall and intermediate level of surfing, will a 6'3 be fine?

Answer
I think that sounds fine, although it's not really a lot of information to go on. If the surfer (you I presume?) is of average build, fitness and surfing average waves (by this i mean 2-6ft ish) this should be fine. Width of the board also factors though. You need enough volume to float you so make sure it's not too narrow (compared to the other boards in the shop etc.).

Intermediate surfers usually have a much better idea of what board to ride and will have already bought a few - I would class intermediate as surfing in up to 6ft in green waves out the back, turning, cutting back and other manoeuvres quite confidently. In this case such a board would be okay but it's impossible to tell exactly without knowing the other dimensions and more about the surfer. Hope that helps anyway and if it's a bargain, go for it.