I will practically guarantee you that your stock pump can get to 100 psig. That is the design. If it can not produce that pressure, your pump is failing or there is a restriction.
It comes down to believeing them or believing Ford. I will repeat - Ford specifically states in literature that risking injector o-ring failure can begin at 75 psig. There is no question as to the meaning of their statement - it is specific.
IMO - The wise person will be conservative. Running OVER 60 psig will get you absolutely NO benefit (this is not a 7.3L diesel). The only thing you need is to ALWAYS keep the pressure over 45 psig since this is the leading cause of injector damage (low fuel pressure - another Ford statistic). More pressure does NO good. You want enough pressure so that at WOT you will not drop below 45 psig.
Do what you want, but it is an expensive risk.
I hear you bismic. When my new spring gets me way over like yours was, I'll probably choose to buy a new stock spring and try out the BB mod(if necessary). But like I said, I want to check it out like you did. I'll get to see how my 7 yr. old pump performs w/ the new demand. Thanks for the heads up.