I've been looking at bed to tire clearance as well. My brother said he would allow 5"-6". He said you'd be surprised how much distance is needed when you hit a bump with a load on it. I have a '59 one ton with a flat bed on it and it does have about a 5-6" clearance.
I'm putting a '59 8' bed on my 41 and don't want go any higher off the chassis than I need to. I do have a decent pair of fenders if you are interested and I'm about 3 hrs. from you. I plan on using the '41 fenders on mine. But we're not supposed to talk about selling anything in this section or the moderator will get mad at me. So PM me if you're interested.
~ Victor
1941 3/4-Ton Pickup (in process). Read about it
in the DITY Gallery1955 Grumman Kurbside "Doughboy" 235/3 on tree w/ OD
1957 3100 - moved on
1959 C4500 Short Bus "Magic Bus" - moved on
1959 G3800 1 Ton Dually "Chief" - moved on
1958 C4400 Viking "Thor" ~
moved on to fellow Bolter