My apologies for the delay in replying, although we received a similar inquiry via contact form around the same time. Hopefully, we answered your question. However, in case we didn't, here's my reply to your question:
You might not need wheel spacers. If you want/need them, know that most of our customers get the 31mm DRA Series wheel spacers by H&R.
That said, here are different variables to consider in determining the spacer you'll need/want.
Pick a brand that's well-known with a good reputation for quality. We like going with the German brand, H&R because we have a history with them as providing us with quality spacers that no one has ever complained about.
Two types we commonly see are those that have the lug bolt go through the spacer, and the other type is one that has the lug bolt onto the spacer. We use H&R's DRA Series spacers because you can take the currently-installed wheel lug bolts and reuse them. Here, you bolt the spacers onto the wheel hub, then you use the lug bolts to bolt the wheel onto the spacer. This has a range of thicknesses from 20-45mm. We prefer not to go over H&R’s 31mm spacer because we feel that beyond that starts to create a little too much leverage. You may still be OK, though with 40mm or 45mm.
We don’t have this down to a science yet, but sure – as your tires get beefier, you may consider giving your truck a more pronounce aggressive (wheels “pushed” outward with spacers) stance to go with it. In part, the choice for how thick the spacers should be is a matter of aesthetic preference. In part, it has to do with utility. If your tires are not starting to rub a bit in the wheel well when you turn the wheel, it’s possible that spacers will help with the issue, but we can’t guarantee it. It may depend on tire size, what all is down there in the wheel well and how close those parts are getting…. It might even be affected by slight differences in shape of the wheel well.