All 737s ever made are certified under
one "type certificate," originally issued in 1967 and updated or "amended" for each new 737 model introduced ever since. To that extent, "a 737" is "a 737," and that document covers all 10000+ of them.
http://www.b737.org.uk/a16we.pdf
You can track some of the changes over 51 years through that document - primarily those that affect airworthiness: "can it safely fly and carry passengers?"
I have no idea if there remains any parts commonality between a B732 and a B37M - whether one can swap a panel of nose skin, or a particular gear-strut hydraulic valve, between them. Probably not much - but I could be wrong.