My 240s never had an arm rest, and the sunvisors are melted from its time in Florida.

I was wondering if I could use some interior parts from another car, Volvo, BMW, or something else that'll fit.

I can't get any 240 bits at my local yard, battered examples are being scrapped less and less. And my spare sedan sun visor parts have the wrong bolt pattern/ arent wide enough to grab the "hook". Yes you can swap in 940 seats, but not 240 sedan visors, just weird imo.

Arm rests are pretty darned rare, only ever seen one. I was wondering if I could take a center console from a 940 and fit it in there along with the arm-rest/pocket.

 

the 240 center arm rest was a option sold at the dealer parts counter, probably long in since unobtanium.

the 740/940 center console box is integrated into the whole parking brake, shifter, center dashboard piece, I doubt you could use only one part of it. further, the stock 7/9 center box was really too low to be a useful armrest, there was an aftermarket thicker top replacement for the lid that raised it 3-4" and made it a more useful armrest.

 

Figures, I only found one once on a dark green 240GL sedan, installed it on a regular 240 I ended up selling.

I was thinking of trimming it a little, but I know what you mean about the weird armrest shape. The one I had access to was pretty narrow/low.