Anyone know what it is? Could not find it on the website.

For those interested, BS is -4.61" and offset is -10 mm. I saw these with 285/65/18 BFG AT's and they stuck out only about 1" in front and were about even in the rear. With all these wheel questions, we could really use a knowledgable (sp?) wheel vendor on this site!

I was going to say -4.5" and -10mm based on my (sorry) memory, but you've already answered.

So what is the right back spacing for our trucks, looking to do some serious upgrades in the next 2 months ( Lift & Tires Wheels, Exhust & tuner), & do not want to do the trial & error routine!

It depends on the look that you want. Generally, if you want the wheels to be inside or even with the wells you should go with 5 or more inches on a 9" wide rim. If you go with less than 5" they will stick out some.