I own an '83 245GLT, M46, 283K miles. You don't state whether yours is manual transmission, so I'll assume it is.

Outside of the previous post, off the top of my head let me list other expensive items:
- suspension, front and rear: examine bushings, front struts and rear shocks. Chances are several are bad. I redid all bushings and struts/shocks myself.
- turbo might be vulnerable to failure (expensive). I've had mine replaced
- manual clutch won't last forever, I've replaced mine a couple of times.
- transmission: shift linkage may wear (mine did)
- engine/drive shaft/transmission seals leaking

Many other parts I have found in junk yards. Actually, the car was beginning to morph toward '93. Outside of a needed paint job, car did well and was fun for me to drive.

Hope this helps.
Mike
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'83 245 GLT, '92 245DL, '90 760 GLT