So I just got meself an Ibanez RG-560 from 1987.

I love it, but single coils aren't really my ting, at least not in the neck. Routing in order to fit a full sized humbucker is not going to happen. I need suggestions for a neck humbucker that sounds as fat as possible. I don't really need something with extreme clarity like evolutions, I have that in my other RG. It just needs to be warm, fat and pretty high output.

And here's a pic, just in case anyone would want to see the beauty!
(it's got a cliplock dimarzio strap now)
Guitarist and composer of the band SHADOWMIND. Check it out:

The hot rails would work. I have had the Seymour Duncan LIL 59 in my neck slot in my 2 electrics and it keeps up output wise with my JB Sh-4 and Distortion pickups. I absolutely love the fat sound the lil 59 gives me for neck solos and sounds great on the clean channel. I play everything from Metal to blues-ish stuff and it does both very well.
My Gear:

Fender Strat w/Duncans
Hand Built(by me) guitar w/Duncans
Ibanez RG321MH
Bugera V22
Peavey Vyper 30 Watt
Xotic BB Preamp
MXR Carbon Copy Delay
Digitech Hardwire Chromatic Tuner
Fender T-Bucket Acoustic
Digitech Bad Monkey