There's a new one out there, Eminence makes it, it's supposed to be the "best thing yet to a vintage Jensen"... it's called the GA-SC64. Guthrie Trapp (Nashville monster player and tone lover) was talking about it on FB.... he's a vintage Fender guy, he plays a Princeton, Deluxe, or Vibrolux 99% of the time... famous for his tele playing.... "this is THE best replacement speaker for Fender amps, I've been looking for this speaker for years!"
disclaimer: he is endorsed by Eminence, but he's a straight-shooter, and very picky about tone.
I've tried the Eminence GA-SC64 (actually tried both the 10" and 12" versions). Love them both. I can't say how them compare to a vintage Jensen, as I've never played through one. But compared to the current issue Jensens, I like these much better. They're warmer but still chimey. And they seem to hold up better at all volumes.
Agreed, @Professortwang. I have a 10F150T (25W model) in a '68 PRRI. I use it as my "Americana" amp, meaning it breaks up nicely, and fairly early.
I'm still debating on what to install in a '65 PRRI, however. Jim's recommendation for the Celestial G10 Vintage is well received, and currently at the top of my list. But I'm also chatting with Mike/Magic Amps and CJ/Weber Speakers to try and decipher what their proprietary design is for the Vibro Prince and Vibro Deluxe amps. How this conversation does/does not unfold will probably make the decision for me.