I was under the impression that what DPowers and Vectorit has was used for the 67-68 283 and 327 are correct... take a look at this site:
http://www.am-autoparts.com/AM/Exhau...-/AM-28014528/
The style I have was used more often in the early to mid-60's trucks and in most corvettes. If you have the same setup I have, then you should only need the angled pieces to secure the top of the alt. by bolting it to the intake manifold like DPowers last pic shows.
Can you post a pic of the exhaust manifold that's on the truck?