Your spacer thickness, wheel backspace, and width will all need to be considered together. With the welded inserts you can set your own backspacing, and eliminate the spacer all together.
My main negative with the spacers was the same as the two piece wheel, and runflat insert I cut out with a chain saw. These trucks do not have a lot of horsepower, and any increase in rotating mass deducts from that hp to the ground.Being able to spin and clean out all 4 tires is critical in red Alabama clay. Keeping fuel cost to a minimum is a plus too.