Doug Hewson used 2mm mild steel on his 5″ EIM wagon Bruce.
This scales to (nearly) 1″ in real `life, which I think will be correct for ‘W’ irons. As far I am aware, most wagon ‘W’ irons did not have any addittional “wear” or bearing surfaces.
I am sure there are many books which give details of RCH wagons but the one I’ve always used is the old MAP publication “Private-owner wagons”. Not sure if this is still in print but I quite often see them in S/H bookshops. The ISBN is (was) 0-85242-343-8, it’s only 48 pages but will give you most of what you want for RCH wagons.
The EIM (Doug Hewson) 5″ wagon series started in March 1987, but part 3 (May 1987) will give you most of the key dimensions.