[ricola]

I've experimented with header tanks up front but much prefer them at the rear. Worst case if you get air in your system, the last place you want it is in your heads/thermostat so I would always keep it at the back, a small bore pipe from the top of the radiator back to the header tank will keep it bled. Unless you are using a strange radiator set-up the engine tank will be the high point anyway...