Bought replacement rear caliper, because of a stuck piston. The old caliper has a brace, or metal stop, bolted to it. It appears that would "connect" with a large metal piece attached to the body when the shocks are fully compressed. What is the purpose of this thing?

My problem is that the replacement caliper seems exactly like the old one, except there is no place to bolt on the metal brace. It was really cheap on ebay, I hate to send it back, but don't need a new problem either.

thanks for the help!

also, what is a good anti squeek for the brake shims? I have some red tacky spray stuff that does not seem to work.

make sure you have the same brand caliper. I'm not 100 percent sure but I have never seen Girling rear calipers with the deflectors. I have only ever seen them on ATE calipers. The two brands look very similar when rusty. The best way to tell them apart is by the hardware. The Girlings have hairpin clips to hold the pins in, and the ATEs don't.
It does not really matter which brand you use, but I would want them to be the same brand on both sides. Its easier to change the pads on ATes. Around here the Girling hardware rusts so badly you need a hardware kit every time you change the pads.

The metal braces on the rear calipers and body are for rear impact control !
helps accordion the body metal outwards away fron passengers inside. Brake fluid flushes every 30K helps to prevent caliper piston freeze ups, as well as premature master cylinder leakage. Dot 4 recommended ! Brake pads and shims
receive a light coat of Volvo synthetic paste part # 1161037 after a caliper fitment check ( aftermarket pads may need slight dressing on contact edges)
where they ride on the caliper body , top & bottom ! the same paste goes on the mounting pins after they've been cleaned up on a wire wheel. Again if using after market pads make sure they have a 45 degree bevel on the leading and
trailing edges. Inspect the rotors and clean off excessive rust. BG makes a product called "stop squeal" basicly graphite with and alcohol carrier. This is applied sparingly to the pad surface and rubed in and allowed to dry prior to instalation. I'm sure they're other manufacturers out there check with your local parts store or ask the dealer when picking up the paste.

Thanks a bunch for the explanation of the need for the protuberance on my caliper. I will sadly return the cheap ebay calipers and continue shopping.

Question - "Again if using after market pads make sure they have a 45 degree bevel on the leading and
trailing edges" So the pads should have a chamfered edge on the breaking surface at the leading and trailing edges? Mine are aftermarket, but not "cheap" pads.

Thanks again. All of this information is appreciated.

That's correct, and also true for the front pads ! i forgot to mention also clean the calipers where the pads rest,with a small wire brush ,if they're just dirty, and a small file if rusty ! Also the brace is primarily impact absorption as Ken stated , Crash, Catch, Buckle, it all happens so fast ! !
Happy new year

Hi. re: "...The metal braces on the rear calipers and body are for rear impact control! helps accordion the body metal outwards away fron passengers inside...."

Yes, it's to protect the passengers from a rear-end impact. But what that piece actually does is provide a connection to dissipate energy in a less harmful or destructive way.
In the event of an impact, with the rear structure being pushed forward, that "fan-shaped" structure (that you'll see just rear of the brake caliper's protuberance) will engage the brake caliper through its protumberance (i.e., the brace or stop that you referred to), which in turn is strongly bolted to the rear axle. Thus, energy is directed into the massive rear axle (whose great mass can safely dissipate a lot of kinetic energy) rather than into the passenger compartment's bulkhead and safety cage. The fan shape, being vertical, ensures that the two pieces will engage each other regardless of whether the axle is high or low at the time of impact.

But as 'trick-bricks' pointed out, you'll want to use the proper caliper (the ATE), which has this feature in order to maintain the crashworthiness that Volvo originally built into the car.