Well, having read this thread, and seeing Dane's response to my other posting on thread "Adding an HB1 to a 4003"
viewtopic.php?f=2&t=406346&start=30#p776376
I'm going to modify my 4003 and my 4001 to identical spec: HB1 bridge, 11k Hi-gain (adjustable poles)in the neck. All 4 pots will become 500k, with a .022uF tone cap for the HB1 and a 0.047uF cap for the Hi-gain.
I have a spare 500k push/pull (that I never really used, from the 4001), so I may wire it into one of the basses so that when it is pulled out, I coil tap the HB1 AND put in the 0.0047 vintage sound cap together, (kind of a double hit, but I'm sure I read here somewhere that the vintage sound cap with an untapped HB1 isn't so great!)
Happy to be called a plonker, if anybody thinks I'm wrong, and happy to receive further advice/suggestions! Of course I'll keep the original pickups form the 4001 nice and safe in the same box as the remains of the original pickguard, the horrible old tuners, and all the original corroded screws/mute bolts.....! (I don't throw any Ric bits away!) I can always reverse the operation!
Luckily the 4003 has evolved from an eBay carcass so no worries about replacing "original" bits.
VC