When to use pinion shims?

[oneprblmcat]

When would I need to use pinion shims when lifting the rear? At 1", 1.5", 2", etc? And which way of lifting the rear would be better, shackles or blocks?

I recently added a shell and I'd like to bring it up in the rear a bit. The truck came with a Revtek leveling kit in the front, but I don't know what size the kit was. I measure the spacer and adapter at 1 1/4" total but it looks like it also compresses the spring a bit. I haven't had any luck identifying what size I have in the front. Any suggestions as to what I might have up front and what I need in the back will be appreciated. Here's a couple pics if it helps.

Thanks

[oneprblmcat]

As I'm thinking about this more, maybe an add-a-leaf kit would be better with the extra weight of the shell and a futuer rasied bed set-up inside? Any recommendations with the add-a-leaf?

Thanks

["00"Tundra]

Tundra Shopping Cart for Toyteclfts.com I have this AAL in the rear of my truck. The change in ride quality is minimal.

[oneprblmcat]

I'm leaning towards the AAL now. Thanks for the link.