I believe there are two versions of the red stripes. The old style (junkers) that shot a big single stream of fuel like a garden hose, were actually 40's.
The newer ones (different MFR) was a 38#, with a nice conical spray pattern.
I took 36# blue tops to high 11's, with room to go further. The same injectors went 11.6's in the car I bought them from.
But as was already mentioned, it depends on how hard you want to push 'em, per duty cycle. I'd say mid 11's is far enough with them.