Almost any "modern" dash will not look right in a G-body. That Jag dash included.
The G-body has sharp, angular lines to it that a dash with a lot of curves just doesn't match or fit in.
However I prefer the custom touches that don't scream "hey, look at all the custom stuff I did!" but rather you would need to spend some time looking at what was done.
And in my opinion, there are very few modern dashes out there that match the lines and level of luxury and detail found in the Olds dashes with their wood grain, chrome accents, etc. Especially something from a a low level F-body.