At 6'4" your proportions become more of a problem. As "Scotty" Thompson says in his book "So you're going to wear the kilt" it is better to have a kilt too short rather than too long.

I am fairly short in the torso, (for my height) so I take a kilt longer than the usual off the peg 24" (I am 6'5"). If your inseam is between 32 & 33" then the 24" kilt would probably be OK.

I would go with one of Rocky's (USA Kilts) which will be long enough and of you get the PV will be washable.