John...currently i ve outfitted 2001 GMC 3500 cargo,the seating is excellent good lumbar support, matl, very comfortable. They use a 1 in . thick "wool batten matl" followed by a 1/8 in. rubberized type "floor mat",very sturdy matl cant cut it wth a razor knife i had to use a heated tip knife to cut her! Works extremely well for sound deadening. The cargo area i replaced with the 3/4 plywood,along with the etrack of course all gaps were filled with silicone...The cab i left alone as it has the forementioned wool etc...i used to haul insulating firebrick,OTR a tricked out straight truck,longest allowable, a GMC stretched brigadeer had two tag axles,year fails me 80 maybe,good ride,"ok", sound quaility 10sp.(13?) roadranger if my memeory serves me correctly,just the right amount of turbo etc...recently ive driven the 94 (yr) Ford series day cabs oh heck cant remember the exact series,VERY nice!...Ill go to my old employer and get back with you on that...( ok did that,they were the L8000 series,with Ford diesels,actually think they were made in brazil, Hmmmm 7.6,six cylinders ) Before that internationals ,they were not in the ball park as far as sound goes,SCREEMERS or sure! Another 99,jimmy, she was fine also.Now they have the Sterlings ,they were gratious enough to let me take one out,VERY nice! ...Driven a D series fl70 99 and was NOT impressed at all, the cab design is way to cramped and noise would be a problem, unless theyve improved the ergonomics since 99 i just cant go there ! Reminded me of the ol uhaul rental truck cabs...When i get my D unit Im thinking i might go with a stretched tracktor,then i wouldnt be limited to weight either...i have not looked at the newer used FL70s i hope theyve improved them! Of course no complaints about Alumibunks sleepers,condo,nice for sure! Ill be back at ya...Since driving the Sterling, welp im thinkin, ill go with one of those IF the expediting industry is all its seems its cracked up to be ! Yours W.R. P.S. feel free to P.M. me!