QST Magazine, published by ARRL, Dec 1998 and Jan 1999 has a two-part article on building a 13.8 V, 40A switching power supply. Maybe you can use this as a starting point to decide if you want to do it or not. Often these articles include information on parts, printed circuit boards, etc. There is a link to these articles on the ARRL website, but they are accessible only to ARRL members. If you know a ham he might be able to access the .pdf files for you, or you can buy reprints from ARRL, I'm sure
You can probably find more power supplies articles if you go to ARRL website and search the QST indexes.
Also the ARRL's Radio Amateur's Handbook generally has some power supply construction articles in each edition. These may be available at your library.
Hope this helps.