Small Block Edelbrock Intake - Which Thermostat?

I have a Performer RPM intake for my 360. I bought a thermostat for a 1976 Warlock 360 [which is what it's going in] and its too small, it falls into the coolant passage way.

Which thermostat do I need? Earlier ~1970's small block?

I think you got the wrong thermostat from the parts house. 79 was the changeover year, which is the smaller style.

Earlier one yes, 180 or above