plug that hole and use one of these........
http://www.jegs.com/i/moroso/710/63423/10002/-1?parentproductid=744342
ouch!!!!!!!!!!
This is what I used but in the fitting on the other side of the the thermostat housing, seemed a little deeper.
http://m.summitracing.com/parts/atm...sj2sMYCFQgtaQodKWQN3w&ibanner=MobileSwitchYes