Thanks, X's are what I had available(and freshened)so that's what I used.
Lol, those cc's may be in print, but both @CFD244 and I have measured with widely varying results.
J- 65 ccs but some say maybe up to 72 ...
X- 63 ccs...
other than that ports etc. very similar if not the same.
OP looks good. better to do it on Js than x heads I do believe the X heads are more desirable being the early 340 head.