Definately need universal joints!! And if you want to make life easier for you, just get new bolts/nuts. Don't try to get ones matching the stock bolts. Just get bolts that are a little smaller than the stock ones. Then use an open end wrench to hold the head of the bolt, and put nuts on the bottom. But get fender washers and lock nuts. You don't want them coming out!
For removal of the collecter nuts, you definately need u-joints. The 3/8 u-joint is an imperitive tool!
Also, how did the bolts break? I mean, did the nuts get stripped? Or did the actual bolt break off? Did it break off before, or after the nut that is attached to the bolt itself. If the nut is still there, you can get a deep socket, and unscrew the bolt from the collecter flange.
Scott