The wiring will be present in the trunk for the antenna and the signal from the radio that causes the up/down to work. On our 240's there is also a Green wire in that area that has a constant 12V and one of the leads for the antenna is spliced into this.

The challenge will be to cut the proper hole in the proper place in your fender. If you can find a 240 with a power antenna, use that as your template.

I have seen plenty of these in the junkyard and they all look the same to me, regardless of model or year, maybe Volvo bought a boatload. They look like a Metra-44PW22 with a "Volvo" sticker. But the one in that eBay ad doesn't look original to me, could be aftermarket. The wires are not the same colour as the OE Volvo ones I've seen, and look like a lighter gauge. Funky connectors, too. The unit may have been pulled from a 240 Volvo as the seller says, but that doesn't mean it is an original Volvo unit.

You can still get the Metra brand new with guarantee from places like parts-express.com for $45, so the eBay pricing seems a little aggressive.
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Bob: son's XC70, dtr's '94-940, my 81GL, 83-DL, 89-745(V8) and 98-S90. Also 77-MGB and some old motorcycles.