Thanks to Rich Camarda all of the 256KZ's U39 can easily be recreated.

There are two methods, one is getting a bipolar PROM burned using the tables included
The other method is to use a PAL/GAL programmed with the table using a modified socket to fit.

There are 5 U39's, 947 is the most common.
947 is one 256KZ board providing 4 banks of 64K.
948 is for two 256KZ's and goes in the first board and provides firs 4 banks.
949 is for two 256KZ's and goes in the second board and provides last 3 banks.
950 is for one 256KZ and one 64KZ providing first 4 banks and the 64KZ as the 5th.
951 is for one 256KZ and two 64KZ's (5th & 6th).

You can also use 948 with one 256KZ and three 64KZ's.

There are 10 files included in the archive to use 5 hex dumps to create a PROM and 5 for PAL/GAL's.

There are two photo's showing the modified GAL socket and a 256KZ with one mounted.