The Rally dash thread

OK, To pick your brains...
I have a '69 Barracuda for parts, dash is complete with a/c and am/fm thumb wheel radio.
My intention is to convert my '70 Swinger standard dash with a/c to the Rallye style. Buying a re-pop '70 Bezel and modifying the '70's wire harness (9 circuits i think) to accept the Rallye cluster and connectors.
I may have a line on a '70 Rallye frame (rusty) or should I use the '69 and fill the ignition switch hole or what? Am I totally off base? What am I getting myself into? HELP :?