I'm looking to replace the EMG-HZ (passive) pickups that came with my ESP AX (basswood body). The guitar is pretty messed up (repaired neck, lots of dents) so I'm looking for a cheap option.

I've been looking at getting GFS crunchy pat/rails (for neck/ bridge) and was wondering if anyone had experience with these pickups or this setup.
This guitar will pretty much sit in drop C for metalcore/melodicdeath. I play mostly out of a Peavey 6505mh through a 1x12 v30.

Thoughts/suggestions welcome!

You're probably primary, if not only using the bridge pickup yes?  You can pick up a used EMG 81 for under $50.  A couple 25k pots, a capacitor, stereo jack and battery cable all for under $20.  Boom, metalcore.
Used sites are your friend here and I agree with Xander_X to start with just the bridge pickup if you can't afford both.  Look into Seymour Duncan JB, Distortion, Black Winter, Nazgul, or one of their other hot humbuckers.  
Jackson Kelly KE3 - MIJ (Distortion/Jazz)
Jackson DKMGT Dinky (EMG 81/85)
ESP E-II Eclipse Custom (JB/'59)
ESP LTD EC-1001FR (EMG 81/60)
Fender MIM Strat

Mesa/Boogie Dual Rectifier Roadster 212
Laney IronHeart IRT-Studio
Peavey Vypyr 30
Peavey ReValver Amp Sims
TOOOO many T.C. Electronic Pedals. . .
I'm using a GFS Fat Pat on bridge, it's very hot and articulate, I don't do metalcore but judging from this you may have a good time with crunchies. But I went GFS because I couldn't find used Duncans here, and going used could be better for you.
Really happy with the Crunchy PAT. Both guitars I have it in are in Drop C, and were a great upgrade. Outside of stock pickups, I only have long-term experience with the EMG HZ 4A pickups in my Schecter. From my experience, they are clearer and more articulate than stock stuff on a Squier Bullet and Washburn RX10. For $22 a pop, it's worth consideration at the very least. 

You could also e-mail GFS and ask what they'd recommend.
Schecter: Damien 6/Stilletto Extreme 5, Squier: Bullet HSS*, Washburn RX10*/WG-587, Agile Septor 727

Peavey: Vypyr 30/Max 112 (200W), ISP: Decimator

Quote by dannyalcatraz
Understood- I waste money on amps*, too.

justinguitar.com is the answer