I have a dash out of a 71 monte,non gauge,w/harness,i have a horizon dash,i was wondering how hard of a swap it would be and what would i have to do,thanks,72 velle.

71 dash harness will not work with 72 engine harness. It can be made to work but you will have to reconfigure the terminals in the bulkhead connector. You will need wiring diagrams for 71 and 72 to see how it is different.