The parts that I have collected so far, for my future 604 build.
Almost mint MP C barrel
NOS Colt slick side upper, that is the later, round forged with black lugs.
A Nodak Spud 80% lower "partial fence", with Colt engraving.
And a Colt Parkerized "slick side" bolt carrier/ gas key.

Two questions:
#! Should I use a chrome, or parked bolt?
#2 And with the "partial fence" lower, is this collection of parts going to be a mixmaster?

I know that by looking at the sticky "Upper Builders Guide", the pre 67 Lower isn't correct for the 67 & Later Upper components
I'm wondering how the "transitional period" might come into play.

Nice parts, I'm a purist so I would use your barreled upper on a proper full fence lower with a forward assist BCG.  Save that lower and carrier for an older build

I'm doing a transitional 604 build right now with very similar components. Mine is a round-forge slick-side upper, parkerized slick-side carrier, and when they get here, a "partial fence" lower and CMPC barrel.
I was told those would be correct for a transitional build so I don't see why yours would be different.

Nice looking start!

I'm no purist and I am partial to partials and chrome BCGs!

Use the "Schwartz" JeepDan! What does the "Schwartz" tell you to do?

ALWAYS follow your Schwartz! Has he ever lied to you?

Air Force ARs have historically been mixmasters. In 1979-1981, I was in a USAF Reserve SP flight.  We had a green stocked 601 in the arms room, GAU5-A/As, and GAU-5/Ps.  My GAU-5/P was on either a 601 or 602 lower, as I had the non-captive pivot pin.  We had some 604s, also, and even a couple 603s with forward assists.  Almost ANY configuration would be correct for a USAF weapon!

Jeep sent you a IM with a couple qustions