TC made .45 and .50 cal hawkens, but probably phased out the .45 about 20 years ago. There's a .45 Hawken on Gunbroker now, clearly showing pictures of the TC logo and the 45 cal stamped into the barrel. I've seen web references to .45 Hawkens with serial numbers in the 8000 to 14000 range.
I'd bet TC hasn't changed the design of any of the lock or trigger assembly components ever. Your .45 barrel (and corresponding barrel channel in the stock) is likely 15/16" across the flats which wouldn't interchange into a newer TC stock for a 1" across the flats barrel.