a way for a godzilla and pacific rim cross over to work

It's not another dimension that they're from. The Rift is indeed a dimensional gateway, but between entire universes, not dimensions. So, basically, Pacific Rim was the result of their completely different universe trying to conquer our completely different one.

ah so it was different universe thing. so do you believe it could still work out like that?

Doubtful. If anything, the Multi-verse theory has no real bearing on how things work there. The Anteverse works on almost entirely different fundamental laws of physics compared to the mainstream universe where Earth inhabits in Pacific Rim.

It's highly unlikely that their universes work on alternative outcomes of an origin point to create a multi-verse, and instead each one is unique and with few similarities.

There's already one universe with Earth, there probably isn't another one.

This could work.

I think if a Godzilla and Pacific Rim crossover is made, it should be made after Legendary and Gareth Edwards have completed their trilogy of Godzilla movies. Then, if they so desired, Legendary could reboot Godzilla within the Pacific Rim universe and go from there. That was what was essentially done with Batman. Christopher Nolan's trilogy was completed, and now Batman is being rebooted in the same cinematic universe as Superman.