Astec AA21660 power supplies can be modified to give 13.8V / 24A.
They are specified to 24A @12V and 27A @5V, with 400W max continuous power. It is used in various Engenio (former LSI Logic) storage products, which are OEM-ed by many companies: IBM (TotalStorage DS4xxx and DS5xxx line), NetApp etc. The IBM FRU is 19K128.
The following mods change the overvoltage protection to 14.4V, and set the voltage to 13.8V.