4" to 4.5" Bolt Pattern on a 7 1/4" Rear?

Hey Guys, I'm new to this forum, currently own an '06 Daytona, but got the itch for some good 'ol nostalgic Mopar. I just bought a '68 Cuda Fastback with 10" drums all around. I got my hands on a '74 Duster front-end, to do the disc conversion. So here's my question, After I install the front-end parts, I will have bbp in the front, is it possible to change just the rear axles & drums to the larger bolt pattern, or do I have to swap the entire rear to something else. I have always turned to forums for help, and have never been let down, thanks in advance for your help, Rob.

look for a 8 1/4 out of the 73 and up A body V8 car for big bolt pattern
most 8 3/4 will still be small bolt pattern and very expensive, if you can find one