The rims are decent and if they are properly laced to good hubs they should provide good service. Check the condition of the brake tracks for noticable wear or scoring.

As to the freehub capacity, a Shimano 7-speed freehub body measures about 30 mm from the base of the splines (the shoulder where the largest cog sits) to the end of the rotating shell. An 8/9/10-speed Shimano freehub body is about 35 mm measured the same way.