She may be correct about the rotors. Early 740s had a one piece rotor when shipped from the factory.

Later on, a new adapter hub kit was needed to install the new hubless rotors. This car with the low miles may have had the rotors turned or replaced soon enough after new to have used orig. oem.

If it has the orig. one piece hub/rotor system. I would get new front spindles from a newer year car, new rotors. Calipers might be different too.

I would research it more online first. It could be a major issue to convert; especially if you don't have a garage or the tools/time to do the work.

Check for rust in the wheel wells of the trunk and where the 3 corners of the inner footwell, the firewall and wheelwell meet.

Not only is the engine wiring harness biodegradable, so is the tranny harness.

Sunroof? Check for leaks and clogged drain tubes. Check the windshield and heater core by feeling the front carpet for wetness. Not sure, Pull the carpet if they will let you.

Check the condition of the replacable parts and if you can determine the brand name of the part. Such as oil filter (brand can tell if home change or SnappyLube) Belts/water pump may tell if serviced by Volvo mechanic.

I'm going to assume that the engine seals are all original and you should plan on replacing them. Low miles over many years; the seals get hard and brittle.

Parking brake may need to be serviced. You will need to check the shoes and the cables. At the very least; I always have to tighten them a little bit.

An '86 is an old 740 and they are a dying breed. The wiring harness is the older style and isn't compatable with '89 on up. '88 Series is the one you can use to replace any wiring harness you may need.

If memory serves me correctly; you may have to swap wires on the grey connector at the firewall to convert an '88 to an '86/87.

Good luck and you could probably get it real cheap because of the age and if you can point out some of the defects it may have and what it will cost for you to replace/repair (hopefully you can do it yourself and save a lot of money.)