2466 123 is indeed an A904 for a '65 273 A-body, so whether or not it's the original transmission to your car, it's the correct kind for it. Yes, it'll work fine behind the later engine, but you'll need a 1/8" spacer ring to fill the space between the '67-up crankshaft's large counterbore and the '66-down torque converter's small nose. You can't just put a later torque converter in the early trans; the pump drive splines (etc) are different. You can do it with some parts swapping, but it's easier to just get the spacer ring. You can get it from Torqueflite specialist Pat Blais, (206) 365-1966, who can also sell you all the stuff you need to rebuild and beef up your '65 904.
While you are at it, a nice, sturdy new deep pans with unwarped rails for the can be had as Chrysler part № 52118 779AD, and they even include a spiffy magnet to catch metallic shavings. Save yourself a bunch of current and future hassle: Discard the floppy cork or rubber pan gasket that comes with the filter kit (remember, your '65 trans needs a 2-port filter, not the '66-up 1-port filter). Fetch Chrysler's own really nice double-seal, reusable rigid pan gasket № 4295 875AC.