Hi. Having owned a '73 164 and currently a '75, along with a string of 240's, I can't agree 100% about the interior. The '75 164 is the only one that's fully interchangeable (viz. the interior) with the 240's; while the '74 and earlier were more like the 140's (that isn't to say, however, that certain 240's parts won't fit anyway -- it's on a item by item basis -- some will, some won't).
However, about your '74's brakes:
The front rotors are distinct, strictly a '72-75 164 item, not the same as the 140's, or the 240's, parts. Likewise, the front calipers are a unique '72-75 164 item (no match to 140's or 240's).
The 164 rear rotors for only the '75 interchange with all the 240's for years on -- whereas your '74 164 rear rotor matches to all 140's and 164's that are '67 to '74, but not to the '75 164. And your '74 ATE rear calipers (they were Girling only '69-71) match with 164's from '72-74 ('75's is different), and 140's from '70-74.
Here's the breakdown of p/n's for your '74 164 (from Volvos' Quick Reference Parts Catalog, dated April 1990):
front rotors: 270735-4
rear rotors: 270731-3
front calipers: 5002018-9 (L), 5002019-7 (R)
rear calipers: 5002002-3 (L), 5002003-1 (R)

Hope this helps.