Help on how to replace upper control arm mounts

The inner fender is full of holes too. Based on that rust line across the whole shock tower and both mounts there isn’t going to be much left of the top section of frame rail either, that was the water line for all the junk sitting up there and
it was all sitting on top of the frame. Once you get down into it I suspect you’ll find the top of the frame rail is trashed too.

There’s no trick to this, you’ll have to cut stuff out until you get to the welds you need to get at. Assuming the mounts just don’t take the upper parts of the frame rail with them.

Measure and mark EVERYTHING. If you get the reassembly wrong you’ll never be able to align the car. I’d set the car up so it’s leveled and supported on both sides of the area you’ll be working on, you’ll need to pull all the chassis measurements like in the shop manual to check everything when you reassemble it.

As for the car remaining complete while you make this repair, I don’t think so. There’s more to replace there than just the control arm mounts and shock tower. The inner fender will need to be sectioned at least, it’s full of holes there behind the shock tower and mounts. On the bright side sectioning the inner fender back will get you more access. I’d pull all the sheet metal. Fenders, hood, latch panel, all of it. You’ll probably find more rust when you do. This isn’t a small job to be done quickly, especially if you’re doing this on both sides. That’s going to be a fairly significant structural repair by the time it’s done. And it includes all your front suspension mounting points, so it will have to be fairly precise too.