mtv wrote:...You'll note also that a lot of the things on the C170 TC are pretty much standard on the 150 and 185, for example Vacuum system and gyro instruments. ....

Not necesarily. I don't have the original equipment list for my 150D, but the one I do have (for a 150E) shows gyro's (item 110) not being required, not being standard, and in fact not even installed on this particular airplane when it left the factory.
This being my point, you need a copy of the original equipment list as well as the TCDS to see what's legal & required. The list (items 1 thru 216) are pretty much what's shown for the 170 on the TCDS. It'd just be nice if it was all on the TCDS just like for the 170, so you'd only have one "go-to" document to check.

Eric