D1 wheel pattern
 

Is it possible to replace our pattern from 5x6.5 from my D1 to a 5X120 system from a later model d1 or d2? Obviously replacing the Hubs.. but are they interchangeable?

Later model D1, no such thing. All D1, RRC, and D90 have the same hub pattern. And no they are not interchangeable with D2s. But D2 and P38 are interchangeable

You can get adapters, but they're pricey and I can't think of a reason to do it.