Someone recently gave me an old Airco 180A stick welder; AC only, but contiunuously adjustable and a very wide range. It doesn't have a power cord or switch, and I've not had a chance to see if it works yet. Assuming that it does, I'd like to add DC capability; I'm thinking about trying an external bridge rectifier using 1N3737 diodes (Powerex) which are rated for 250A and 400V each. But at $32 each, I'd appreciate any input before blowing that (pun intended). Is there something better and/or cheaper?

Try some surplus silicon power rectifiers instead. 250A 400PIV are 4 for $70.

http://www.aaaim.com/cgi-local/shop991/shop.pl/SID=208807250306/page=TRNS.htm#PD8971