Grabbing a DP slider over the holidays, and I need some advice on what heads you guys are using for this.

Must be able to support a 7D, with grip, and a 70-200. Guessing a Manfrotto 498RC4 would be acceptable?

Manfrotto 498RC4 Midi Ball Head with 410PL QR Plate 498RC4 B&H

Any other recommendations?

I don't use a ball head instead I use this fluid head.
Manfrotto 128LP Micro Fluid Head 128LP B&H Photo Video
They also have one with a QR plate

My main concern is being able to adjust for angles. I plan on running the slider on 45* downward slides to emulate a little bit of a jib motion. That head doesn't allow for an angled adjustment which is why I was thinking ball head.

I do have a tripod but it is a 65mm bowl head and I dont think there are any sliders that can make that work.

Just mount the adaptor plate on the 7d sideways and you can use the fluid head for all sorts of angles.
That's what I do with an old Manfrotto 501 head.