In the rear. Don't forget the purge valve on the thermostat housing. I will be running a huge 3 pass 2 core in the rear of mine with twins 5500 cfm. If I were you with the build your getting I would run rear without a doubt. I used to be against it, but was forced to make it work for my 454. It worked sweet. Never above 190. Ran at 160-180 all the time. Hooked the fans into my F.A.S.T CPU and it worked flawlessly. I was very happy with the result. The only bad part was the cost of the fans and radiator and the aluminum fab work to mate the 2 together. All well worth it though! Good luck!