I've had good luck cooking large chickens at higher temperatures. Put them into the oven "feet first" and side by side. There should be several inches of space between and around the birds to allow for heat circulation.
Roast them @ 450 F for 30 minutes, turn the temp down to 375 F and go for another half hour and check the thigh temp.
If you like, after the first half hour, make deep cuts between the leg/thighs and the chicken's body on all sides. This allows heat into the area inside the thigh that's the last place to get done.
"If you want to make an apple pie from scratch, you must first create the universe." -Carl Sagan