Y,
When you say blocking diodes, you're talking about a rectifier? Typically people either buy a "potted" bridge rectifier or, build a stud-diode rectifier. The potted types are simple, inexpensive but probably not as robust. If your building one with diodes you will probably need some sort of heat sink material to help keep them cool, but this can sometimes be integrated into your housing/box. I'm assuming this is on the ground. Perhaps if you can clarify your application it will help.
~ks
