Easy - it would be like the CEs or older Customs with toggle. Assuming one volume, one push/pull tone and one 3-way toggle. I would follow the 3-way toggle wiring diagram used for CEs and older Customs. I'll attach it below. This is the easiest layout to use that allows splitting, also be sure to use the capacitor and resistor values that PRS has in the diagram. The resistors, in particular, are necessary when splitting the humbucker...the singlecoil tone is boosted/strengthened by the added resistance and helps avoid a weak, piddly tone when in split mode. PRS uses those resistor value across most, if not all, of its pickups (I've confirmed that with PRS when swapping untold numbers of pickups).
Check your pickups...McCartys have singe-conductor vintage-style braided wire. PRS uses an extra wire (usually white) for the coil-split. If you have that wire you are all set.
If you haven't done it before, it helps build a template of the control cavity out of cardboard or masonite. Attach the pots and secure them. That gives you nice platform to work around the components and help ensure you are giving sufficient wire slack in the circuit. Wiring inside the cavity comes at the end when you make you last connections - output jack ground and hot, bridge ground, and pickup leads.
For the resistors on the tone pot, I
highly recommend wiring those on first, before introducing the pot itself onto your template/board. One end of the resistor lead solder to the middle lug. The other end grounds to the pot casing. Don' t trim the resistor leads until you are happy with how they are secured. If the pickups have four-wire leads (i.e. designed for the 5-way blade switch) you can still use them...just solder each pickups ' untapped coil wire to ground (one PU's red wire, and the other PU's green wire to ground).
You can get fancy and wire push pull for both the Volume and Tone to alter series vs parallel or other combinations. Personally, my favorite is 3-way toggle with single push/pull. More than that makes my head hurt.
3-Way Toggle / 1 Vol / 1 Push-Pull Tone
#1a Humbucker
#1b (Tone Pulled) Humbucker Singlecoil
#2a Humbucker & Neck
#2b (Tone Pulled) Humbucker & Neck both Singlecoil
#3a Neck
#3b (Tone Pulled) Neck Singlecoil
Parts
Volume - PRS 500k (made to spec by CTS or Bourns), including 180k treble bleed capacitor
Tone Pot / Push-Pull - 500K, Audio taper (PRS uses Alpha, I prefer Bourns)
Tone Cap - .033uF (PRS uses axial film caps - the best match to OEM spec is a Mallory 'mustard' polyester film capacitor)
Toggle Switch - Switchcraft 3-way toggle (PRS uses the 'L-style' right-angle version - the short-body straight switch also fits, but slightly more annoying to wire)
1/2W 2.2kΩ Resistor (Carbon Film) - To bridge PU wire coil-tap lug on push-pull pot (1/2W will work, just smaller than OEM spec)
1/2W 1.1kΩ Resistor (Carbon Composition- To neck PU wire coil-tap lug on push-pull pot (1/2W will work, just smaller than OEM spec)
*Note: Resistors in tone circuits are usually come metal film (blue), carbon film (tan), or, less-common, carbon composition (brown). PRS uses carbon composition resistors for this circuit. Carbon comps are harder to find...I recommend Amplified Parts or Tubes & More (same company). They will have all the other parts, as well.
