Need Headers Installed in Boston
I did Doug's on mine and TTI's on a buddies Swinger. Both about the same. A lift would do wonders as far as time involved. Both Z-bars needed the inner arm cut off, repositioned inward and rearward. TIG'd em back together and good to go.
Also you'll be cutting the "ears" off your bellhousing. No big deal.
Don't forget you also have to drop the front suspension. Either company will be happy to mail you the instructions to check out before you dive in.
Don't expect either one to admit the z-bar thing. Search this forum for tips in that issue.