Well, for memory the more the better; if you can afford, max out your system. If you're on a G5, 2 gigs of RAM should suffice although you only need 1 gig of ram to run FCP5. I'm shooting a feature as well in 1080/24p and although I have 2 gigs of RAM in my G5 now, I'll be bumping up to 4 when it comes time to edit.
I think you might have meant storage in regards to editing... Just in case, that 8-1 ratio would yield approx. 720 minutes of footage. 1080/24p is 1 gigabtye per minute. I'm planning on getting a LaCie drive to hold all my footage, they have a 1.0 TB(1,000 gigs), 1.2 TB (1,200 gigs) and a 2.0 TB (2,000 gig model) now available. You might be safe with the 1 TB drive but if you're worried, get the 1.2 TB drive. They are around 750 to 900 dollars if you purchase them through Apple with an educational discount.