Like the title says, would it be possible to replace a old worn 80's kahler tremolo with a new one.

The tremolo is a old original cam system. It was retrofitted onto a string though dean bel air I'm thinking of getting.
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Yeah, I believe so, I can't see that the routing is going to be that much different.
I'd look online for a routing template for the model you want to get, and lay it over the existing cavity.
They're the easiest trems in the world to install, no spring cavity to rout out in the back, no claw to adjust, no rout for the allen bolts on the back of the unit....

Love 'em.