Cheers for the link! Note that not all pre-CBS have 'L' prefixes for the serial though.
I've finally found my perfect P after owning six. For me the important attributes are (in order):
1. Neck/fretboard playability (tricky to amend if not right 'out of the box')
2. Frets (can be dressed if needed)
3. Weight (may be more important if you have long gigs, shoulder/back issues)
4. Electronics (can be swapped out)
5. Look (probably higher, who am I kidding :))
6. Resaleability (allows you to 'buy blind')
In short, try as many as you can. If buying blind, then buying from basschat means it's unlikely to be a dog and you can resell here if it's not your cup of tea.