So, I called the store back and bought the red set for $583 with sales tax. I'll be mailing out a postal money order Monday, and they will hold the drums until I can return to get them.
I found the Slingerland serial number chart and it appears they're from '68-69.
The plan is to sell the 8x12, both cymbal stands and the Set-O-Matic T tom holder to Kevin, which will probably net me some nice $$. I also have a few other pieces of drum stuff to sell, including a stripped Ludwig Jazz Festival shell and some hardware. Between all that, I might come close to covering the cost of the set.