From what I can gather the front trunnion holes on a Vulcan receiver have to be made oblong to slide the barrell assembly forward acomidate the magazine. could one remove some of the magazine hole AND some of the trunnion holes and have the same results, to keep the barrell assembly from possiably moving?

Yes. If your worried about ovaling the holes too much for a good rivet hold you can do that. A screw build is not as sensitive to the condition of the holes in the receiver. As you've probably noticed the as drilled holes aren't lined up quite right -- the trunion dips to the front slightly. I put two together, a '74 and a '63 using the predrilled Vulcan locations -- had to trim the front of the rec. to get the hanguards on right. To fit mags, I took metal of the rear of the mag well and then fit the catch to the mags. Both function fine even though there is an ever so slight dip in the bbl (not visible to the naked eyehe
Keep an eye on the ejector. Mine wore slightly but stopped after 40 rounds. I didn't harden it successfully. If ejection problems ever show up it'll get the TIG treatment.

Hammer, did you have to grind your ejector down to fit? My bolt will cycle but the rearward motion is tough to say the least. Do you think I should grind it down or let it wear off?

For a 7.62x39 you do need to take the ejector down some. It is the right size for a 5.45.