If you look in the archives of 17 Dec. 2002, John Tempelton had the AFE listings for all the changes to the K-28.
The AFE for doghouses for K-28's came first for #474 in 12-31-38. No. 472-475-476-477-479 came 12-31-39. No. 470-473-475 came 12-31-40. No. 472 came 12-31-41.
These dates are probably not the exact dates they were applied, just the dates they were authorized for.
Other postings by John Tempelton in the archives can show the dates for the K-36 and K-37. I think the K-37's received them some years earlier.