I show MCA 1970 Concourse Driven and this comes up occasionally. I present my spare facing down as that's what I think the trunk decal shows (to me it shows the back of the rim with the small flanges facing up, back side of the rim). But the decal is a repo and its a little on the blurry side and some judges aren't convinced. I have attached a copy of the Ford 1970 Mustang Assembly Manual, Body, page # 78. Here you'll see that it states "valve side down" for "Reg Prod Conventional wheel" (steel rims) and shows face up on "RPO Styled Steel wheels". You'll also note that the "Bolt" for the steel rim is a different part # (C8AB-14498-F) as opposed to the Styled Steel Wheel, which is a different, longer bolt (part#C9ZB-1448-D). The Manual states "D0ZB All", which I interpret as all body styles.
I did present this once to a Judge that questioned my placement, and his reply was that the "Assembly Manual is not always correct". With that rational, then why assume the trunk decal is always correct and why refer to the Ford Assembly Manual for any refences at all. Another Judge stated he wanted the spare mounted face up, so he could verify that the spare was the same as the tires on the ground (whitewall and correct stripe, etc.) regardless of the decal or other information presented. In all fairness, I don't believe I suffered any point deductions, but have had it noted on judging sheets as an item to "correct".
At the end of the day, its all good, and I get to play with Mustangs, but be prepared however you decide to go.
