It took me a while to figure out the difference between 250k 500k and 1000k ohm pots ...
the first bit of information I got was here ...
http://www.stewmac.com/shop/Electronics,_pickups/Potentiometers_and_push-pull_pots/Potentiometers_and_Push-Pull_Pots.html
then the next bit of information I got was the Rickenbacker schematics that showed the volume pots were 250k ohm and the tone pots were 500k ohm ... the current schematic on the Ric web site shows the current configuration of 330k ohm volume and tone pots ...
then the third bit of information was an email from John Hall who told me that in the 60s, 70s, and 80s Ric used 250k ohm volume and 500k tone pots ... in 1990 Ric switched to all 250k ohm pots in the 4000 series basses ... then in 2005 or 2006 they switched to 300k ohm pots ... (and John thanks for that info)
Then I finally understood why certain basses sounded the way they did ... I had wondered why my 1989 4003s5 was so much brighter than my 1990 4003s5 bass ...
pots have a big impact on the sound of the bass ... for instance if your 4004 sounds too dark then put in a 1000k ohm tone pot ... if your 70s 4001 sounds too bright then put in 250k ohm tone pots ... if your 4003 sound too dark then put in a 500k ohm tone pot ...
The .0047 capacitor removes low frequency response from the bridge pickup ... so it really doesn't make the bass brighter it actually removes bass response from the bass ...
there were 3 basses that I experimented with pickups and electronics changes. The first was a 1973 4001 that I got off ebay. It was all screwed up. The pickups were good but it was rewired all wrong. I put in 4 250k ohm pots and no .0047 capacitor. it sounded great. Then I rewired a 1976 Azureglo 4001 for Steve Cooper. It had a pot that turned backwards and a dead neck pickup. I put in a neck toaster and rewired it with all 250 k ohm pots and no capacitor. It turned out to be the best sounding 70s 4001 bass I ever played. Then my 1968 4001 had the original horseshoe pickup and the original toaster pickup. The old pickups were degaussed and weak. They lacked balls. So I left in the pots, bypassed the capacitor, and put in 2 4003 pickups. It still had a ton of treble bite but now it also had 4003 growl. It sounded awesome.
So an easy way to make a v63, C64, or 4001cs sound more like a 60s 4001 is to put in 2 500k ohm tone pots.