Hey Dan, I was taught that the 8mm PMM was based on the 308 Norma and was done a fair bit even before the 338 came out, could have been misinformed. The 8mm-06 though was never called the 8mm poor mans magnum, that much I do know.
To bump it up to a belted case requires a bunch of rail work, to get them feeding properly, as well as the bolt face work. I built my first 257 Bee on a completely original VZ 24 rifle in 8X57 JS. It turned out to be a lot of work as it was my very first project when I was 18 years old and working under the supervision of an old German 'smith, who was a perfectionist. No dremel tools in them days, it was all done with his set of stones (he wouldn't let me use the mill as he said I should learn the proper way first and there was also no chance of wrecking the action with stones as there was with the mill). I also lengthened the magazine box on that VZ and made the floorplate hinge and latch, removed the stipper clip ears with a file and made it match a commercial 98 perfectly............It was a lot of enjoyable work !!!
It taught me patience I had previously never envisioned possible.
Sorry OP, got off on a reminiscing tangent, remembering an old friend and mentor who has long since passed.