fleetsides long or short are 'rarer' than stepsides, simply because it was an extra-cost option that most didn't think worth the $$ - I like fleetsides, which is why I have a long one, and why I bought a 'loose' short fleet box some time ago to put on my short truck, which is currently a stepside
OTOH, I much prefer the TF Chevies to the GMCs - don't like the GMC dash or grill, but that's me, if I found one cheap, fleet or step, I'd no doubt want it
Bill