So I was looking at my 68 trim tag and it has a 10c build date was that in late 67 or 68.? The car is a factory RAM air 1 according to phs

If you 68 firebird was build 10C that would mean 10th month C week.

We would call that an early build 68 built on Oct. 3rd week. 67

Should be a March 68 built date...("C" as the 3rd month)

No 10 is month and c is week on the body tag.

https://firstgenfirebird.org/1968-info/1968-technical-information/1968-body-tag-information/

So wouldn't it be third week October but was it 67 or 68. If it's like new cars it would be a 67 of October date right

Correct. Oct 3rd week 67. Like I said in first post.

Months were 01 to 12...weeks were A to E. A being first week...E being last week of month. 10 C.

42nd week of the year..October 1967 had 5 weeks. 10C would be a build from October 15 to 21 1967 for the 1968 model year.

Your drive train dates would be roughly late Ixx7 September 67 to Jxx7 October..cast into block, heads, rear, intake, manifolds.

Ya drive train was Mia when I got the car