Wiring harness from '73 into '72?

[AZkick-n40]

Starting to do some work on the '72 to get it on the road. Noticed the PO did some hacking to the wiring harness. I have a '73 that I am using as a parts rig that has a clean harness.

Any reason to NOT put the '73 harness in the '72?

How challenging of a task is it?

Any words of wisdom from others who have done the same thing?

Thanks,

Brian