The very first thing you need to do is confirm what the problem is. Get that jack (Get a nice big jack with a lot of lift, and a wide removable cup. It's nice to have more than one jack, too. I have two bottles of different size and an old Sears hydraulic jack) and those jack stands (I've got monster ones so I can lift the car nice and high). Put it up in the air, remove the wheels and look around and feel around. You should be able to find out what it is.
If it is indeed the control arms, get the Factory 5s as suggested and install them yourself. If you don't have an impact wrench, which seems likely, make sure you have a good breaker bar with a cheater pipe and lots of penetrating oil. It's likely that the fastners are pretty rusted by now.
There's always a first project and this is as good as one as any. I've always used the money I would save on installation to buy tools. It may cost the same, or even a little more, but it will be a lot less the next time around. I bought my air compressor and impact wrench when I did my springs. I couldn't get the nut off of the top of the strut without it.
To raise the vehicle the easiest, block the front wheels and slide the jack under the differential housing. Jack that up until you can slide the jack stands under the frame rails on each side just about where the mufflers are. I put them behind that flat piece of metal that connects the frame rail to the body. Let the jack down on the stands and then give the car a shove or two to make sure everything is solid.
Good luck with it.
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351W 89 Mustang GT Convertible