Ford sized the stock pulleys the way they are for a reason. You want an engine that runs hotter than normal, and doesn't keep the battery charged? Go with the underdrives.
Never had a problem with them at all. But had a good rad, but a stock pump. Put plate on the back of the impeller in the pump and would run 160 deg in 120 heat.
I had underdrive pulleys in my truck and did nothing but kill batteries and run hot. Youll notice March has even added a super cool waterpump pulley from all the complaints they got from cars running hot.They even say "normal charge after 1500 rpm....." so if you sit in traffic or cruise,your gonna start killing the battery if the rpms are less then 1500.
I've run UD crank and H20 pump on a few different vehicles w/no problems in the Phoenix heat. I use a big radiator, Mark VIII fan, hi flow pump and don't use the alt pulley. You can always use just the crank pulley.