for a start, what car is it
i used the older, 1.9, more simple thermostat on my opel gt with 2.4 head. however you can buy or make, i made, a plate to go behind the thermostat in order to bring it forward as the fi gets in the way.
this is an adaptor,
Too pricey for me so I made mine similar to this plate but if I remember it had a different no. and position of the mounting holes.
This is prob as im using a cut down 6 cylinder inlet manifold and not a 2.4 or 2.0, 1.9 one.