For a 1975 164, basically most things (including the rear suspension, rear brakes, and almost everything in the passenger compartment) is "early 240" -- most folks say "everything behind the firewall". The most notable exceptions are about the fuel system, which is more typical of 140/164 components; and it has 240 style, but nice upholstered leather seats not found in 240's.

In front of the firewall (front suspensions, steering, brakes, and of course the engine), a lot of it is typical 140, but some things are unique to the 164 series, of course; and, unfortunately (speaking as a fellow owner of a '75 164), a few things are unique to that year 164 as well.

A 164 is a nice "project" car, if you have the time and inclination (as you can see below for mine).

Good luck.

Ken
'75 164, w/ factory power windows and sunroof, BW-35 (the one "negative"). This one is 49-state version, without catalytic converter or unleaded gas restrictor, but it has a smog (air) pump, which I will remove. Also, I added Rallye-/GT Instrument Cluster, IPD antisway bars, and 16" alloy wheels. I'm also working on (as a winter project) fender modifications to allow installation of 5.25" round high beam headlights in the "horn grills" under the 7" headlights (Cibie's).
Repainting and reupholstering are last on my to-do list, behind some mechanical work.