I don't know about the g8o in a 14 bolt but as far as the trans cooler goes, there are a lot of people on here who have had good luck with a 28k GVWR cooler from B&M. I stepped up to a 40k from Trucool and never see temps over 165 even in 100+ degree heat. Not to mention, I might have an extra 28k B&M trans cooler laying around!!!