In 1959 and 1961, seventy _IZ_ wagons were rebuilt with welded bodies using components from the _HY_ ( non grain proof _GY_ ) design. These modified open wagons were recoded to HZ.
There was already a _HZ_ van in service for use with the weed spraying train. This van was recoded to _WZ_.
The numbers for the HZ group were:
6 - 8, 11, 22, 25, 27, 28, 33, 39
42, 58, 60, 65, 66, 68, 74, 81, 88
94, 104, 107, 111, 113, 118, 121, 125, 130
132, 136, 138, 155, 156, 168, 179, 180, 192
194, 197, 205, 216, 228, 251, 252, 286, 295
301, 326, 333, 337, 340, 355, 358, 368, 393
406, 410, 415, 438, 447, 495, 499, 516, 530
549, 563, 567, 762, 793, 804
From 1961 through to 1966, these wagons were progressively recoded to HY. As HY wagons they were converted to GY wagons in the 1966/67 program. The wagons were incorporated into the GY number block 911 - 1160 along with other IZ conversions.