We left exactly what Best recommends and provides for with the tool kit. I'd guess 60 thousandths but I don't know really. The kit number is 5144. Also, Best makes an EXCELLENT pan gasket and I highly recommend that too. Much better than the FelPro pan gasket.
If you look in the photo above, you'll see a wooden "thumb protector" for trimming the seal ends and it is shown in my post "in use". Under the knife blade (included in the kit) is the black shim which is also shown as a round end on one end and recess on the other. The recess is fitted over the seal end while lying flat on the block or bearing cap, then the wooden thumb protector is used to cut against. The trimmed seal is shown in the final shot of the bearing cap.
