[Brian]

Well done! my heavy old 35 sedan with waterpump in heads 21 stud and 3.78 ratio bum will regularly not go any faster than 79 MPH in second gear. Doesn't blow up either!
I read it on the 'net somewhere; I think it was about Arkos Duntov, about how they realised a flathead runs outta breathing before it gets into dangerous revs, therefore was an ideal platform to 'modify'. So...with this information I regularly put it to the test. Sure enough...they get to a max speed and will not go beyond it. What the absolute toip speed would be, I can't tell you, roads in NZ are not long enough, and I'm too chicken!
One thing I do know, the 284 I built and put into the same test rig 35, did not go as fast as that little 221. That longer stroke just will not rev out the same.