Welcome!

I don't know about your car, but many Volvo radio systems have separate amplifiers - find out if yours has one as if it does, a radio swap is not straightforward.

Volvo turbo engines are quite different from non-turbos - just adding a turbo is not an option.

If you want a turbo, you may have to find an aftermarket system (if they exist) of find a motor swap including computer, all sensors and wiring at a minimum.

Your best bet might be to find an inexpensive parts car with a turbo and a stick shift. You could save a LOT of time and money having all the parts and documenting how the systems come apart. You might even satisfy your mechanical wanderlust during disassembly and leave your sweet survivor alone.

Unlike most. I had 740s and 850s with turbos and think that they are well suited to automatic trannys. Jump on the pedal, downshift, and go! I think that the automatic slippage allows the turbo to hit its sweet spot sooner.