After consulting with Magnetic Reference Laboratory, I did find that
broadcast alignment cartridges are still in their catalog and readily
available. However, this is "Fidelipac" (4 track compatable) format,
not 8 track. They currently offer the ITC carts, same as the old
ScotchPaks, but you'd still have to transfer the spool into an 8 track
Scotch cart to make it run on 8 track machines. 3.75 IPS is a
non-standard speed for broadcast carts, 7.5 being the standard for
decades, but they do indeed offer these, as well as 15 IPS. EQ is NAB
open reel, with 3180/50 µS equalization, but there are options for IEC
cart, IEC open reel and still other manufacturer-specific EQs, such as
Otari. I believe that 8 track carts were NAB 3180/50, but I'm not
entirely sure. The NAB standard for cartridge EQ were first released
in 1975, but there's no supporting documentation that this is what
consumer 8 tracks were EQ'd at, and no one at MRL knows for sure.
Anyone have a clue here?

These are available in both full track, the normal alignment tape
format, and "program/cue track," used with Spotmasters and other
broadcast cart machines using various cue frequencies. Fringing
compensation is also available, which is desirable doing freq runs on
a multi-track machine. Reference fluxivity, however, isn't per the 8
track standard of 185 nWb/M, and the closest they offer is 200, which
is .7 dB above 185...NOT a problem. You could also opt for 160, the
same standard as early cassettes, which would show up aroun 2.3 dB
below 0 VU. These are all offered on lubricated backing cart tape
stock, so they should live awhile. Now, as to which existing 8 track
carts will accept an ITC spool, I'm not sure yet. One major problem
of 8 track as a format in general was the lack of any realistic
standards at all. Philips knew this when they set about converting
their "dictaphone tape" format for music, and laid out iron clad
physical standards for anyone using their cassette format under
license. Hence, cassette was a far less problematic format to deal
with than 8 track.

dB