You may have trouble with a 48" bar when it comes to straps. I mounted a couple of 52" bars to early 90s F-series using long gutter straps but had to move the feet to the edge of the frame & get longer screws that attach the strap to the feet. I do not know if you are going to be able to strap that bar to that truck. Why don't you just bolt it straight to the roof?
if you double nut and lock wash it aint goin anywhere. i had my hawg up to 90 with them like that. sucked gas to do it though. Nobody cares for looks vs. functuality. sometimes you gotta do whatcha gotta do.
I used the threaded rod trick with some roof top carrier strap kit. I slightly modified the gutter strap mount for my 47" mx7000 on my 93 f150 reg cab (silver roof, narrower roof also) and on my 94 ext cab (blue, wider roof line)