....If I go with the 8 guage on the power cables, what is the best way to get them attached to a RigRunner 4005H? It looks like I would need a 75 amp Power Pole connector on the power cables. I don't have the 4005H yet, but from the pictures it looks like it uses the 30/45 amp connectors. The other option would be to just connect the 8 gauge power cable to the IC-7000 power cable directly, but this seems limiting.
Also, would 60 amp fuses be to much on both power cables just down from the battery?
As Alan indicated, a 45 amp connector made for 8 gauge cable needs to be used. Could be that they're a special order. However, I would check the rigrunner itself to make sure it has heavy enough internal connections so as not to be a weak point in the wiring harness, even if the rigrunner specs say "high current'. They still don't put a value to the current spec.
As an alternate, maybe you should terminate the eight gauge cable in a two position terminal block and use three or four pigtail (six inch) ten gauge cables each to its own pair of powerpole connectors from the other side of the terminal block. I also would enclose that terminal block in a plastic experimenters box that can be had at Radio Shack to protect against accidental shorts. When I ran three transceivers and a receiver while I was a member of emergency management for my town, that is how I constructed my setup. If you are going to leave the fuses in the radio power cable harness, that also would eliminate the redundant fuse on the rig runner itself and lessen the voltage drop a bit.
I would think that forty amp fuses (heavy duty ones, of course) at the battery would be more than enough. The primary purpose of those fuses is to protect against shorts in that line and backfeeding from the possibility of a faulty ground connection in the vehicle electrical system. Forty amp fuses would be able to pass amperage enough to feed two or three radios--unless you're going to run lighting or other things off the rig runner. Even then, it's doubtful if forty amp fuses would blow under the load.
In any event, it sounds like you're good to go. Good luck and 73!