Out of my league on the machining end of this, but a 6.5 (.264) barrel blank is not hard to find, it's the grendel/lbc chambering that would be the sticking point.
Probably not too difficult to get the proper reamer, but machining the blank to fit the AK trunnion is way above my pay grade.
The mag comment is an interesting one. AK mags are curved because of the unique taper of the 7.62 x 39 cartridge- and I know there are issues with other straight-wall bottleneck cartridges on AK caliber conversions because of the tapered mags. I would expect there would be issues because of this.
Let us know if you move forward with it, not an easy project by any means but sounds interesting.