Does anyone have information in changing over from the SB heater core to the BB heater core? Can the BB heater core be installed into the carrier with new holes drilled in the firewall for the new location for the heater core lines to come out?

Was there more than 1 Firewall for a 67? There was not. Should be a simple install. My guess is you will have to get the right heater core and hardware. Don't think that when you buy the right unit (core) that is WILL be the RIGHT unit. (Even the right units don't fit in the 67's). The only issue you should have is having the correct "stuff" inside the heat box. I spend a considerable amount of time getting the right heater core. All the ones that the parts houses said were correct were not. Even the ones that looked correct, the in/out tubes were NOT correct.

I have mine out of my 67 if you need any measurements PM me

I took my 68 to a Radiator shop and they removed my old core and built and installed a new core. As a result the fit was excellent and no problems encountered. Kept the same SB configuration.