I have a 1981 camaro Z28 and i want to convert it to a 1970's vintage camaro? what do i have to do?

 

Replace all the body panels from the firewall on forward, and from the top edge of the rear glass on back (including the glass).

 

So to convert the front, i need to replace the front 1/4 panels, and new front nose cone. I assume the doors remain. Now the rear, I need to remove the old 1/4 panels and replace with new and new rear bumper. Trunk okay, what about roof?

 

You'll need to replace or modify the core support for the radiator. Easier to replace than modify. Your hood can be reused, and should be the same if it's not a Z28. The trunk can be reused, and the roof is OK, but the rear window will need to be changed. Take a look at "Junkman's" mods to his.
https://camaroforums.com/forum/70-81-general-12/fiberglass-body-panels-47183/