Thanks timo22. I have them,just seemed kind of long when I checked the thread fit.
If you need replacements...
For the bolt, it's M10 x 1.5 x 30, GM p/n 15592554 and still available from GM if you need one, or 4. List price as of today- $5.23. You can probably find them cheaper elsewhere, but that's the retail price you get if your dealer doesn't give you any discounts.
Everything else is discontinued from GM, but available through the secondary market.
F41 heavy duty bracket for G-body is 14073310. It's the roundy looking one.
Non-heavy duty bracket (not F41) is p/n 406887. This has flange thingies on each side to center the bushing.
Frame bushing for F41is GM p/n 472118, with 30mm (1.18") hole. Per the parts book, pretty much all the other G-bodies without F41 uses GM p/n 472117 (1.08") hole or p/n 370283 (no size given, although one source says fits 28mm bar).