[TA Forbes]

I believe that the two chassis are very similar, the only exception might be the late model 21s that used 45s for output vice the 71s. I only know the model 21 from a friend that restored one, so my knowledge is not first hand. I know Dick also makes cabinet parts for the model 20 radios as well. Not sure if Steve Davis does these models or not, but it is worth checking.
You have two radios that would look swell next to each other after you finish them!