[RamAirBirds]

I should have done this in the first place. I dug out my Pontiac PMI manual with the Engineering drawings for the assembly line. Luckily i have an original that you can actually read unlike the reprints.
As you can see the engineers changed the springs from small #3848272 to LARGE #3907626 on 06/26/70.
So assuming they most likely "used up" some remaining springs they had wouldn't it be a safe bet to say the springs went LARGE in mid to end of JULY?
For sure they most likely used up old small springs but these were on every model Camaro and Firebird so stock depletion would have happened quickly.
It would seem to make sense that many of the RAIV cars then would have the LARGE spring since they were built/shipped July and August?