Good call Matt, no point in letting a Bass go for less than you're comfortable with.
It is a bit of a funny market, the Vintage one, things sell just for what people want to pay for them....so it becomes a very subjective area with regards to original parts etc.
In any case, while you wait, it may be worth trying to source parts from around 1964 to 'restore' the bass, you can never get the finish back obviously, and so you'll always be looking at around half of what a fully original '64 would be, but by adding other original '64 parts back onto the bass, it will no-doubt add value!
Good luck
Si