This is way late but I just found your thread.
I installed Joe Barden Engineering (JBE) pickups in my 4001 to get rid of the single coil hum as well.
They do have a tone that is similar to the stock pickups.
The current owner of the JBE business is a good guy and will return emails and telephone calls.
I discovered after installing them that I needed to jumper around the capacitor on the bridge pickup.
The bridge p/u volume is reduced to an unsatisfactory level with that cap left in the circuit.
I jumpered it rather than remove it to make it easier to return the bass to original configuration.
The output seems a little lower than a healthy set of stock 4003 pickups. Not a big deal.
The bridge pickup in my 4001 was weak and highly feedback prone and was a factor in my decision to try the relatively expensive Bardens.
I had the Duncan SRB-1 pickup set installed years ago in my JetGlo 4003. Still have the receipt, it was Jan. 2000.
I tried them for the same reason of needing to get rid of the single coil hum issue on gigs with fluorescent lights etc.
Although they had a strong punchy tone, great for hard rock gigs, they sounded nothing like 4003 pickups.
I missed that special Ric tone, especially after having the opportunity to A/B with a friend's stock 4003 a few years ago.
So I reinstalled the original pickups and performed the RWRP mod.
That worked as suggested to eliminate the single coil hum so long as both volumes are full on.
I later shielded the pickup and controls cavities. That greatly reduced the hum from EMI sources.
And under the right conditions I can use the bridge pickup only (a GREAT sound) or just roll off the neck volume a bit.
So try the Bardens. Yeah, they're pricey but they do fix the single coil hum deal.
And (or) try the reverse wind reverse polarity mod along with thoroughly shielding and electrically connecting the cavities on your Ric.
Search for the RWRP tutorial on here. It's well written with good photos.