i wish you were closer, i could show you what i am talking about much easier than trying to spell it out. do you have any pictures of the chassis yet?
If you have the hubs that i am thinking about, the extra length on them is what is needed to place the dually style wheel in the correct location. the mount needs to be farther out so that the center of the tire is where it is supposed to be so that the suspension geometry is correct. i do not think that putting single wheel hubs on it will gain you anything in trying to make the track narrower.
now remember, all of my comments are based on what i have messed with, until you actually put a tape on the parts and or set the cab over it, we won't know for sure what you are dealing with. do not get discouraged by over thinking it. like my buddy used to say to me "a little cutty cutty, weldy weldy and you're done" i always thought it was funny anyway.
i have a frt susp setting out that is out of a early 80's 1 ton chevy pickup, i may try to get a pic of it and see if i can show you what i think you will have to do.

do you know the track width of the original? or do you know the measurement from outside to outside of the frt tires?


1937 GMC T16 468 BBC th350, 4.10
1941 Dodge COE 5.9 cummins, 9 speed roadranger
1947 Diamond T COE, hercules and 4 spd, all original
1955 Chevy LCF 9.0L IH diesel AT545
1962 Corvair (Elsie)
1967 Jeepster Commando
1968 K10
1970 Chevy C50 box truck