Generation III External Engine - Need help with water pump?

I am installing the Meziere electric water pump. Using Ls1howto, they show that the thermostat sits inside the housing for the snout. My problem is the old style sbc thermostat will not fit inside of the housing, is there something I am missing, or is it that the thermostat sits on the outside of the pump and I just need to cut the arms off of the original neck?????

ttt......

um why not use an LS1 style thermostat?

The old style thermostat fits in there. If I remember correctly your supposed to drill a little hole in the flange and just drop it in. You need to be sure you put it into the pump properly because you can get it upside down. Then you just screw on the pump output neck that goes to the top of the radiator.