Ray,
For 1967 the "YY" code front spring was used on 6 cylinder convertibles WITH A/C, Base V8 convertibles WITHOUT A/C, Base coupes WITH A/C, Coupe AND convertible 327's with Powerglide and A/C, and Coupe AND convertible 350's with powerglide and A/C. For 1968, the "YY" codes was used on Base V8 convertibles without A/C or Special Performance Suspension, Coupes WITH A/C AND Special High Performance (327 or 396) exec 4-speeds or Special Performance Suspensions. However, the 3905571 number doesn't show up in my books, but a 3905577 does as your "YY" code for 67 and 68. Are you sure about that last number ("1")?
The transmission numbers show this as a Cleveland built powerglide, assembled by the day shift on July 10th, 1968.
Ed
