I have one main e commerce site and search engine ranking is very important.
I also have about 60 other domain names that are relevant to the main domain. example: pizzapie.com & cheesepizza.com.

The question I have is what would be the best way to utilize these domains without getting search engines mad (lose rank). Mirror? Forward? Or should I populate them with the same files? Or same files but change the text around as much as possible?

The last question is basically the same but I also have international domains with the same situation; pizzapie.jp, pizzapie.nz, etc. Would this be any different or does anyone have suggestions how to treat international domain names for ranking in US & the corresponding country?

Plz HELP!

Having multiple versions of the same copy probably won't help. Having different versions (and localized versions for your international domains) on different IP addresses, intelligently interlinked will give you some help significantly.

Best way is to keep them on different ips, as mentioned by Rob, but you also need to keep them in different c classes (aaa.bbb.ccc.ddd, where ccc needs to differ) and you also have to be careful on the interlinking scheme.