I'll need to dig up the part numbers I have for H33 ballasts.... I've got 3 of the waterproofed Advance H33's (these are employed at the moment) and 1 Magnatek H33 setting as a spare collecting dust... let me find you the part numbers and such and we can go from there. And Yup a single WH5 will fire a pair of 65W PC's, though at slightly reduced output, WH5 is rated @ 128w output (99.9% sure this is right, need to double check my memory), the 55 and 65w bulbs are pretty much the same thing, it depends on the ballast as far as their output.