Thermostat for LA M1 intake

I'm in the process of slowly putting my engine and car back together, and decided to replace the thermostat while I had the intake off. When I took off the thermostat housing, I found there was no thermostat in it at all. I picked one up at the parts store, and found its too deep for my intake as it hits the water passage underneath (Mopar M1 W2 intake). Any suggestions?