4 bolts on the inner bumper channel and 3 at the flange connection between the shock and the frame horn, and possibly one more that is attached to an Ell bracket bolted to the end of the shock that fits inside the rear frame horn and bolted to the frame threough the bottom sill using another bolt. They are all Metric, seem to recall them being 11 or 12 mm with either a 14 or 15 mm hex head on them, and the use of 6 point sockets and wrenches along with a power or Johnson bar is highly recommended when trying to persuade them to come apart. Avoid air until you have the nut backed off; applying air will almost guarantee that you chew a head or two off. For the actual swap you need to measure the overall or unsquashed length of the shock, maybe measure the pasenger side, and compare that to the Cutlass item you have. Then make sure the number of tabs or ears that the replacement shock has match the old one about to come out at both ends.
Be aware that the actual bumper channel is aluminum. It is entirely likely that you will encounter corroision or galvanic deterioration due to interaction between the metal shock and the aluminum mounting holes. You may also discover that there are shims between the channel and the shock mounting plate to set and adjust the fit of the bumper and how it sits in relation to the body. Don't breathe that white dust if you encounter it, you are just breathing rust in a non-metalllic form.
Nick