I’ve never heard of spacers or adapters breaking but are the 8 lug wheels a lot heavier than the 5 lug? They were made for a 3/4 ton or 1 ton which usually has stronger axles, diff, and suspension. So you’re increasing unspring weight and stressing those parts a bit more. May be fine though if you don’t tow anything. I used 2" thick spacers once on a 1986 bmw I had, screwed my alignment but I found a local shop that got it right.