Looks like I was mistaken - no ramp on the 84-s. IMHO, I'd just try to wait around for some Norinco mags to pop up. While they can be somewhat hard to find, they're usually not more than $25-30 for the 30 rounders when they do. I've gotten a bulgy .223 mag to work after a bit of filing to fit the mag well, and it has worked 100% so far, but I haven't really put enough through it to say that for certain. They're just as much as original norinco's now anyway.
Given the relatively low price difference between the weiger and original mags, I'd be a bit hesitant to start hacking at the receiver for a conversion that may not work 100%. At the very least, start by modifying the least expensive part - the magazine. While there may not be enough material there to take off enough to match a norinco mag, there is of course some room for clearance. You can probably take enough off the weiger to get a tight fit in an unmodified mag well.
Rocko