Does anyone have an opinion on the quality of the Dakota big bores from the late 1980s? Looking at possibly purchasing one in 416 Rigby.

Make sure the action is properly bedded and relieved at the tang, and that the action screws are properly torqued.

I have seen more than one of them split the stock in that area.

The Dakota rifles made by Don Allen have a reputation for excellent construction. I have two early Dakotas, a .416 Rigby and .375 H&H. Both are very well made and fitted.

I have been trying to sell the Rigby. Comes with 3 stocks.... A custom stock, a composite stock and the original stock. The custom stock is a thing of true beauty. Anyway, I have heard that later Dakotas were not as well made. Specifically those made in the early 2000's (or so I have been told).
There is a lot of rumor posing as fact regarding guns. My suggestion is to examine the rifle and see how well the wood is fitted. That should give you some idea.

I got to handle several that came into a shop I used to frequent in the late 80's. They were very rough and fit/finish was mediocre at best....especially for the price.