You can modify "standard" header bolts from any high performance shop with a "locating boss" in the head.
This allows much more positive engagement and alignment of the headers, and helps to prevent the bolts from backing out.
When you buy the header bolts, they come with a little allen driver to help you get the bolts installed, and then have 12 point heads on them for final tightening.
Design and Execution thanks to the master, Wade (MarkIV/4280) on this board.
See the pictures in this thread, the post is dated 17 June 2014.
Cutting Header Bolts for Better Alignment
Rocky
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.