If you're looking for a complete one piece shooting rest, take a look at the Caldwell Lead Sled.
http://www.midsouthshooterssupply.com/item.asp?sku=00094820216Thats what I use. Rest itself is about 15 pounds, and the gun sits in it, so it reduces recoil considerably shoulderwise. Up to four 25lb bags of lead shot can be added to the tray, to reduce recoil even more. It's about the steadiest rest I've ever seen or used. Some people say that because it's so heavy, it's hard on scopes and stocks, but I've experienced no problems. I did however, line the inside of the rear stock rest with styrofoam type padding, I just felt it was a needed improvement. The rest is completely adjustable front & rear, and is about as close to a machine rest as you'll get as far as steadiness is concerned.
Garry