This is what the guy from England sent me in a email.
"I’m not certain of the size of your original rim or whether it was a drop centre. Your new rim has a drop centre & so the spokes will
Need to be a ¼” shorter for the same size rim. If the rim is an inch smaller in diameter than the previous rim then the spokes will be
½” shorter (less ¼”) IE … ¼” shorter. Conversely if the rim we are supplying is 2” larger in diameter, the spokes will be 1” longer
(less ¼”) IE ¾” Longer. I hope this makes sense!"

Now I see the diagram...and the 70 angle that Buchanan's lists does not match the diagram...the spokes don't look like they are bent to 70 degrees.  The invoice for the rear wheel spokes show they are all the same length of 5-3/4" - then show the angle as both S-80 and L-95 (inner and outer spokes), while it shows the front at 7-15/16" with an angle of M-70.  Something is not consistent about that....as the angle sure does appear to be more like the 50 or so that you listed.

Dave wrote on 02/17/15 at 17:59:37:

Thanks Dave