I looked but couldn't find the answer to that question, I have never counted the splines but if I were to guess I would say your correct, I also think the axles have remained the same. I will see if I can dig further at work.
Heres some info Blackhat620 sent me, the 05+ F350 with the 10k GVWR package has the smaller F250 rear axle, with 35 splines. Member Kep4 has the F350 10k package and his truck has the F250 rear axle
Most 05+ F350 SRW trucks come with the 10.5" Visteon 7280lb rating, 3-pinion (note 5.4L is 2-pinion) rear axle with 1.5" spline minor diameter & 1.57" spline major diameter 37-spline hub end axle shafts.
The exception is F350 SRW SD ordered with the 10k GVWR weight package. These trucks come with the Visteon 6200lb rating, 3-pinion (note 5.4L is 2-pinion) rear axle with 1.36" spline minor diameter & 1.50" spline major diameter 35-spline hub end axle shafts (Same as all F250 SD).
well I pulled 1 axle and sure enough I have 35 spline axles, according to the ford manual, with my gvwr(11,200) I should have had the 37 spline axles? I am glad I have the 35 spline axles now I can put in a truetrac! Blackhat sent me the same info(thanks again Blackhat)but I figured I would pull one anyways to check.