Cant gert thermo gasket to seal.

How is the surface area where the gasket is contacting? Is it pitted or warped? Is the housing surface warped? I've seen new housings warped, so check it good. Are you using a Dodge thermostat and housing, or aftermarket parts?

did you check if you stripped the bolt on the water neck had the same problem couldnt even tell it was stripped tap out to a bigger size but dont drill to deep the sleave only goes so deep and your in the block hope this will help