Seeking mc recommendations

Yes I could change the arm   That would be a fun project

Nice of her. I had a 318 and found it warm and forgiving but it killed the music and lacked detail. The Dual CS505 buried it for half the price back then. Even spending $250 on a AT540ML or 2M Blue will give you an improvement over the old Shure. I don't think the headshell is up to much on the idler Dual. Can you change the arm? 

The Denon DL-110 would be a good choice

The Thorens was a gift from my wife when I started in vinyl. I won’t sell it. I’m interested in experimenting with the Dual since I don’t care for the sound of the Shure M97XE that’s currently on it. I understand what you mean about a cheap MC cart. It would probably sound worse. So the bigger question is : is the 1229 worth putting an expensive cart on it ? 

Get an Audio Technica VM750SH and try it on both the Thorens and the Dual. Then sell the Thorens. I don’t think you’ll gain much trying to use a cheap MC on either.

I had that Dual in the 70s with a AKG cartridge it was my first turntable after my Loddys all in one system

I’ll check it out.  Thank you !

The Dual has a light arm. You can always add mass to an arm to accommodate cartridges with less compliance but in the case of the Dual adding mass is not a good idea as this may affect the longevity of it's automated functions. I think AT's -OC9XML would be a good fit