From the factory there could be 0 speakers, 1 (in the middle), or 2 (one on each side).
There were two types of Instrument Panel Upper Covers (IPUC)s
a one-hole (PN#3590382) - from Marin County
and a two-hole (PN#3590386) - from 76 parts car.
Everyone got the one-hole unless a 4-speaker package was selected in which case you got the two-hole.
The selection of radio didn't have an impact (at least a direct impact) on getting a two-hole IPUC. It was a separate speaker package that got the two-hole IPUC. So someone could get AM/FM stereo, but without the 4-speaker package, would only have a single speaker up front (with a one-hole IPUC).
From the 1974 parts catalog, accessories price list, page 19.
Regarding radios, has the note: > Speakers are not included in Stereo and Tape Player Packages. Refer to Speaker > Package listings for types and part numbers.
Going to the speaker package listings, accessories price list, page 25
For Monaco 4-speaker installations, has the note: > ...use new Instrument Panel Cover, No. 3590 386.
the body section, Pages 23-52, 23-53 show the IPUC as part type code 23-33-22.
looking up the part type code, Text Page 23-34 (pic 2) shows IPUC PN#3590386 for stereo, and IPUC PN#3590382 for w/o stereo.