A while ago I drove my Z into a dark carpark and did not see the island in the center of the driveway hence I ran my Z straight over the top of it and flattened the 2 chassie rails/subframe under the body down from the gear box down.

I would like to fix it up, I had 1 idea to weld 3 strips of flat steel over the damaged area after tring to hammer it out.

Do I need to take it to a panel beater and pay them to fix the rails to get it on the road again?

Can post pic later if needed

I'd say your options are either 1) drill holes through the floor pan and tap the rails out (using a rod inserted through the holes), then weld the holes back up or 2) get hold of a stud welder and weld the studs to the bottom of the rails, then pull them out with a slide hammer. Hopefully you can avoid having to replace them.

http://www.harborfreight.com/stud-welder-dent-repair-kit-98357.html

I will say that this stud welder is not in stock at all stores, but perhaps you can buy or borrow one from somebody.

+1 on the stud welder option. This is a basic tool at body shops, one in your area might weld the studs at a modest price for you to do the slide hammer work.

Jim

One of the Z-shops on the internet is selling replacement rails, that fit OVER the existing rails. They're for 240/60/80, don't know about the Interchange.