Rear swing arm mounting plate, Rusted and broke 1/2 the bolts Options

[tracks914]

The 3 hole mounting plate on my project car (passenger side) is rusted pretty bad so I figured they have to come off for my resto so off they come. They seemed pretty rusted and tight so I soaked them from the top for about 2 weeks with penetrating oil.
Last night I went to take them off but I knew I was in trouble when they were spongy. WTF, grabbed the impact and got 3 bolts out OK and 3 broke off! (IMG:style_emoticons/default/headbang.gif)
Now this is going to be hard to get the broken bolts out. I might have to resort to drilling and re-tapping the holes unless some has a better idea?????Anyone ever have these seized in before??(a stupid question but....)
BTW I now need a passenger side mounting braket (plate) and shim!!
Tx

[ChrisFoley]

I have gone so far as to use a hole saw to remove the metal tube that has the threads in it and replace the tube with one from a donor outer console. Currently I have pieces on the shelf for my raised trailing arm pivot kit that are nearly identical to the factory metal tube. It isn't that hard to cut the welds out with two hole saws and a hand drill, and the tube will come out the bottom.

I don't like the idea of a long through bolt, other than for convenience. Another reasonable method of repair I have seen is using a helicoil or timesert in the lower section of the hole and using a much shorter bolt than original. The most convenient thread pitch may be different than original for this.