If you call a good tool supply shop, you should be able to locate a metric
bottom tap. It will give you the ability to cut the threads a little deeper
in the hole. The one or two extra threads made a difference in my case. I
then used a longer bolt and shimmed it with thin washers to exactly the
right length.

Also, I learned the following trick the hard way. Do not try to force the
alignment of the exhaust pipes to the head even by the slightest amount. If
they are not perfectly aligned with the holes, then disconnect the exhaust
pipe at the "Y" where the left and right sides come together. You should
then be able to fit the exhaust to both head ports with no difficulty and
tighten it down properly. Then you can safely apply a little persuasion, if
necessary, to reconnect the other end of the exhaust back to the junction.
It is easier to persuade that end, and a lot more forgiving of abuse than
the heads. It takes about five minutes longer, but I wouldn't consider
doing it any other way after all the grief I had with stripped head bolt
holes.

**********  John Clavin  |  jjc@bga.com  |  Austin, TX  **********