Simnett: When people mention "Chewy" beer, they tend to mean thick mouthfeel, like a Guinness. Usually they think of heavy, thick Stout beers. And Belgium is not necessarily known for those.
That being said, there are definitely some Belgian beers that have a heavier mouthfeel and taste to it. I would look for dark brown Belgian ales. Corsendonck dark is one that comes to mind. Another one is Pauwel brewery's Kwak. The aforementioned Kasteel dark could be considered "chewy" as well. But none are like Guinness. You can also try Westmalle dubbel. I have some in my fridge, so I know it's available around here. Total Wine in Dallas carries it. And some Central Markets.
With regards to Scottish ales, they are defined usually by more caramelized malts, less hops and a sweeter taste. I know of one true Scotch Ale from Belgium, from the John Martin's brewery, called Gordon's Scotch Ale. Haven't really looked for it to be honest, but the two aforementioned places are good starts. Also Spec's on 75, "Kegs and Barrels" on 15th in Plano, Angels on Jupiter and Plano Parkway or S&K on 75 and Spring Creek are good beer stores with a wide selection.
Lately, with the boom in local Texas breweries, I am stocking my fridge with the local stuff. And some of them are really, really good. And that's coming from a Belgian guy :crazy: