Are you sure you want to be doing this before you've done your research?
8 weeks is fine, 10 could be better but might not be. 8 is certainly a safer and easier choice; the esters will be hanging around for a while longer, anyway. Proviron is mostly to help with DHT and SHBG, it's not an AI, per se. Many are able to cope with arimidex but aromasin or AIFM will likely serve you better.
Take a look through the PCT forum to sort out a protocol for HCG and clomid. My personal preference would be to take HCG starting five days after the last shot at either 1000iu EOD or 500 iu ED. Run clomid at 50mg ED for 3 or 4 weeks starting after the last day of HCG. Run an AI such as aromasin or AIFM from your last shot and through to the end of PCT. If you run aromasin or AIFM as your AI throughout the cycle (recommended) then just keep running it until a couple of weeks past the end of the clomid.
Anyway, you don't give much info about yourself. If you're under 21 you should not do this and if under 23 consider strongly why you'd want to do this to your hormones. If you've not been training hard for at least three years then it's probably still a mistake, even if you're old enough.