Presta valve length

60 mm valve is probably borderline for a 50 mm deep wheel.  Probably depends on the type of chuck you have on your floor pump.  80 mm valve should work fine, but tend to be a little expensive since they aren't as common.

If you're training on these wheels, my suggestion would be to use standard 48 mm or 60 mm valves and just buy a screw on valve extender.  Keep 48 mm or 60 mm tubes in your flat kit, and screw the extender on the spare tube if needed.  It also helps to use some plumbers tape to help the seal, so having your spare tube pre-taped helps as well.

For a race, that's when I'd opt to carry 80 mm tubes as a spare...just so you don't have to worry about moving the extender over, or the quality of the seal when seconds count.

I generally can get 48 mm tubes for around $2 each when buying in bulk and splitting them between other cyclists.  But 80 mm tubes tend to run around $7-8 each.  So over time, it can get quite pricey to constantly replace them each time you flat...but worth it in a race situation.

At least that's my 2 cents.