I am running a '96 cast 351W Lightning short block in my '67 vert with about 6,000 miles on it. Everything said is consistent with what I know about these blocks. The folks at Ford Motorsport tell me, in spite of my wishful thinking or hindsight, it is not a Sportsman block. While I have ran it up to 6,800 RPM (mostly by accident), they say to keep the revs to not more than the early 6,000's. For heavier use they recommend a "girdle" on the bottom end for added strength.
I continue to consider installing the Ford Motorsports 392 ci short block version of the Sportsman block. Maybe next year!
Russ
http://albums.photopoint.com/j/View?u=1595962&a=12199293&p=44747301.JPG