In order of expense:

The kit probably came with four 1/16" spacers (washers). They work, but that's BIG steps, and only two steps at that. Free, or under a buck at the hardware store.

The CRC front ride height shims work well for the Associated arms and the IRS-modified Associated arms (worth the money just for the additional tire life). $8-9. They no longer "notch" these which makes 'em less convenient to use. Notch them yourself by cutting across to the mount screw holes from the "straight" side. You'll see what I mean if you get them. This makes it so you can insert and remove them without completely removing the lower arm mounting screws.

Fibre-lyte (UK) make an excellent carbon fibre shim set that have the coolest looking carbon...it glows. I like that they're measured in mm, IRS rear axle height adjusters, tire diameters and ride height are all measured in mm as it keeps everything on the same page. The .010" CRC shim (roughly .25mm) works excellently with the Fibre-Lyte shims giving a bit more fine-tuning ability. Probably + or - $25 for a set with shipping from the UK, cheaper if several of you order at once (they used to give a discount on orders of, like, 12 sets or so).

If you install the new IRS "lower" arms (NOT the modified Associated arms) I highly recommend the BMI aluminum spacers. The BMI spacers provide a very stable "platform" for the lower arms to ride on as they're held quite a ways above the chassis plate with full-diameter tires. They come in .5mm increments and are chamfered on the "bottom" side to clear the countersink on the lower arm mounting screws that STILL sticks through the top of 2.5mm chassis plates. I use these with the .010" CRC shims also. $60 for all six sets of these. WELL worth the money, imho, I have a couple sets I use among my cars (up to three at any given meeting).

These new IRS arms are neat because you can run the tires from full-cut until the white of the rims shows through if you want. One CRITICAL thing I've found with these arms is that you REALLY need to use a tap (8-32 RH) to thread them. I recommend doing this with any arms, but these it is very important yet they do not mention this in the instructions.

Also, DRILL into your head that ADDING shims REDUCES ride height, REMOVING shims INCREASES ride height. I guarantee you I foul that up at LEAST three times every season. I'm an embarrasment...