I have 2 Bassmans. They never put a crossover in them. I can’t imagine why anyone would. You want a full range speaker cabinet. Check the ohms of the speakers. If they’re 8 ohms just wire them in parallel and get rid of the crossover. If they’re 4 ohms somebody might have put it in there if the crossover made the ohms load in the 4 ohm range. Don’t ever run the amp with less than a 4 ohm load. It’ll cook. 8 ohms is fine. If the speakers are 4 ohms wire them in series. You lose a touch of volume but not enough to matter. The amp will actually sound a touch tighter with 8 ohms. Tubes will last longer and it will run cooler. If you’re using it for guitar it’ll be plenty loud with the best sound you’ll ever hear. I put 4 10’s in one of my cabinets and it kills, even with a bass. One has the original Altec 15. It’s a bit muddy. But using them together gives me enough power to keep up with the band on bass. Looks cool, but it’s a workout hauling all of it around. Thats why the wheel and handcarts were invented.

Back in 1970 I bought a 66? blackface Vibrolux that came with (I thought) a Bassman speaker cabinet.
I have tuned up the amp a couple of times, but the Bassman cabinet just recently stopped working. When I opened it up, I found a crossover on the center cross bar. the speakers were both blue wire on the common to the red dot, and the yellow was hooked to the 2.5K Woofer connection. The 12″ Fender speakers had a part number of 023044. Did someone hack this 50 years ago? Did Bassman speaker cabinets ever have crossovers?

I just repaired a Blackface Bassman head that has a very late 1965 xfmr set (543, 539, 545) with a AA165 label, and rubber stamped “13” (no letters). It has been converted from a bias balance ckt to adjustable bias. The chassis is also rubber stamped “4665” between the bottom of the PT and the eyelet bd. What might the “13” signify? It’s definitely two numbers, not two letters. It’s not the normal two-letter stamp like in my ’65 Deluxe Reverb.