I would refrain from using that amp on any ham bands. I don't know about VK radio regs about CB amps on the ham band, but you shouldn't use for ethical reasons as you'll be transmitting wide, dirty signals to your fellow hams worldwide. It's poor designed, dirty CB amp, which no amount of "filtering" will clean up. This subject has been covered ad nauseum in this forum and the technical reasons explained by persons better qualified than I. Just go to the "Search Forum" box and type in "CB Amps" or "CB amps on the ham bands".
If you are only looking for 30-40 watts out of your FT-817, take a look at the HF Packer Amp by K5OOR at:http://site.hfprojectsyahoo.com/hf_packer-amp
This is a great little amp that covers all the ham bands, and many of the 817 crowd use. If you like, you can easily add a PTT line to it. (More reliable keying under low power input than the RF sensing circuit).
73, Ken AD6KA