ikay

For the neck (J) pickup, the white wire (hot) and the black+shield wires (cold) should just go where the original J hot and cold wires went which should be easy enough to spot. For the bridge (MM) pickup, the white and green (hot) wires should go to the switch where the original black and red wires went. It will work whichever way round they go (eg. white for black and green for red, or vice versa) but the order does determine which coil is tapped. Wire it up and if you're not happy with which coil is being tapped just swap the wires over. (Bartolini wiring code says red is neck coil and black is bridge coil) The brown+yellow+shield wires go to the pot lug where the original white+green+shield wires went.

One thing to watch out for is the number of frets - there are 20, 21 and 22 fret P/J necks out there. Best to swap like for like to avoid intonation and bridge position issues.

Your '87 sounds great, why do you need another one?!

Looks like an attempt at adding a treble bleed cap to the vol control to reduce loss of high frequencies when vol is backed off.

If you want it to sound like a regular single pickup P then it would be best to take the J vol pot completely out of circuit. To do this you need to break the wiring as shown by the green markers in the diagram below. If you leave the J pot connected then the P pickup is still seeing the load of both vol pots which results in a little loss of high end and a slight drop in output compared with a regular P. It's equivalent to running a regular P with the vol backed off about 20%. Not dramatic but enough to be noticeable. Depends what you're trying to achieve by disconnecting the J pup.

+1 All Lakland 5s are 19mm spacing.

It's most likely the TR200 pickups are passive, in which case you can replace them with any other passive pickup. If you want to run a test, disconnect one of the pickups from the preamp and connect it directly to the output jack. If you get a good strong signal then it's passive.

Have you looked on this archive page - https://support.fender.com/hc/en-us/articles/115000819563-Fender-Audio-Schematic-Archive

Yes, that all makes perfect sense.

Yes 500k vol pots would be brighter than 250k.

It's a simple mod but can you post a pic of your existing wiring?

Mmm, if that's the case then I stand corrected. My understanding is that the signal effectively bypasses the cap when the tone is maxed (wide open). The cap only really comes into play when you start turning the tone knob down. The cap then progressively bleeds high frequencies to ground. Not so?

If the tone is always maxed changing the cap won't make any difference.

A no-load tone pot when maxed will be exactly the same as a VV setup without a tone pot. Taking the tone pot out of circuit will be noticeably brighter. By how much is a bit hard to quantify. Instead of a VV setup you could have a single vol control and a three way switch (neck/both/bridge). That would be brighter still. Or you could dispense with pots altogether and just have a three-way pickup selector switch and an on/off kill-switch. That would be even brighter. Removing all of the pots might sound a bit brittle though. Depends what sort of sound you're after. Best way to find out is experiment with a few different wiring configs. The Fender Mark Hoppus model just has a single vol control (no tone) so that might be a useful benchmark for sound.

A loose tuning key? Hold the E tuning paddle when you play the string, see if that makes any difference.

They're still showing a pic of the original 34" hollowbody in the scrolling picture bar near the top of the Skyline Series page. It is discontinued though I think. I've played one of these and really liked it. It had a nice semi-acoustic vibe but was still tight and punchy.

In case you haven't already seen this..

They're not intended to be adjustable but it may be possible. Depends on the construction of the pickup. If the coils are wound directly round the magnets then it's risky, but if the magnet is in a plastic sleeve then it's doable. The fact that your A pole has already dropped but the pickup is still working suggests that it will tolerate some movement so I'd be tempted to remove the pickup and see if you can push it up with your fingers.

My very first thought but I didn't want to be the first to say it! The 1930s is the only one that's remotely got something different, and even then the blurb ( "until now the market has not offered a true high end example of a 30-inch design") is a bit disingenuous. Has he not heard of Serek basses?

The G and E poles should be flush and D and A poles should be slightly raised. Pic of my USA SUB below. These are great basses. The pickup and 2-band EQ on the SUB is the same as a USA Stingray.

Rule of thumb for setting nut height/slot depth is string clearance above the first fret of .003" (top of the first fret to the bottom of the string) while fretting the string at the third fret. That's about the thickness of a piece of paper. It basically just needs to clear the first fret by the tiniest smidge when fretted at the third fret.

It's a Sentell 'Big Sis' pickup, a 4-pole replacement for a Musicmaster bass. They also do a 'Lil Sis' with smaller diameter magnets. See pics below. Website is here - https://sentellpickups.net/bass.html. Scroll about halfway down for the Musicmaster pickups.