M1 Intake manifold thermostat is smaller

[70Hardtop]

Hi, I just bought an M1 Dual Plane inlet manifold. It was new. But the thermostat hole and housing required is much smaller than all others I have seen. It is an LA, not a Magnum. Does anyone know where i can buy the correct vertical water neck (thermo housing) and the smaller thermostat? Maybe Rock Auto? Or any one know of any more Mopar specific places that might sell them? (see comparison photo attached)

Thanks

 

[Cuda4evr]

To me, it looks like it would take a t-stat for chevy. I ordered an high quality(expensive) t-stat for my 440, it was to small for the six pack intake, but fit a small block chevy edelbrock intake I had