I love the m110, which I've only had in the euro forum. I love a w116 in full Euro dress (lights and bumpers). If this thing is a running euro for $1500, I would not hesitate. I understand that the US spec engine of that era (and even the earlier carbed US m110 engines) moved along pretty well. So maybe despite possibly having lower spec HP, they could be just about as good as the Euro. I don't know.
It's hard to turn down a good running car at $1500. Can you enjoy it as is?
Many will say, there's nothing more expensive than a cheap Mercedes Benz.
The m110 is a solid lifter engine and should have valve adjustments every 10,000 miles. You may not want one of these if you aren't handy or have a good relationship with your mechanic. Of course all that depends on what you want to do with the car too.
Past mb: '73 450sl, '81 280slc stick, '71 250, '72 250c, '70 250c, '79 280sl, '73 450sl, parted: '75 240d stick, '69 280s, '73 450slc, '72 450sl,