I did the JB weld thing two years ago.  Since that time I have logged about
20K miles and so far all is well.  To paint a picture for you, my heads were
both extensively pitted.  I didn't measure but some were probably 1/8 inch
deep by 1/8 inch wide.  I don't know of a better repair other than to replace
the head. The JB weld was certainly an economical repair Vs. the cost of
replacement.

I used two different sealers when I did mine a black type on the heads and
yellow on the head nuts.  I obtained them from my local dealer for about $20.
The part numbers were D 000 400 01 and AKD 456 000 01.

Chris
2  86 westies