KEN - Gator makes blades for the 44" & 50" decks since all three blades are the same length. But on the old 38" & 42" decks the center blades are the same, just the tiny outer blades change length which it seems like the out blds on a 38" deck are something like 9 to 9-1/2 inches which has to be the shortest blade on ANY mower deck. I'm like you, ain't walking out to the shop to measure.
I kept seeing ads in FARMSHOW magazine about some sort of blade that was a round disc that had four sickle mower sections bolted to it. BEASTLY expensive too. Somebody across the tracks put a set on another brand tractor. Last word I heard was, "They're GREAT, Bolted right on fine!" But he never got back after the mower cut any grass.
I find that if I keep the blades really sharp, and try to have the tractor running straight when mowing both my decks do a decent job. I think the 38" deck mows just a bit nicer than the 50" deck but it takes a lot longer to mow with it.