Sounds like I should drill the passage way ...

Sounds like the simply way is to drill the passage way to the cross over first.
I only have a MIG welder, no TIG. If I grind down the portion above the threads, I'll probably snap the tap off deep in my block...

I'll check my taps and see if I have one that will work. Production tool supply is about 25 miles away. Gas is $3.47 a gallon here. I'll see what I have on hand first.

Thanks again to all of you for the help.

Cheers.
Danford1