Setting the correct degrees on engine and rear end

I will be using parallel leaf springs on my 51 Chevy 3\4 ton and see that 3 degrees down on both trans and engine is the proper setting. What is the best way to determine those degrees? Is there a tool I can use?

Use an angle finder, available at some parts stores, and in all the tool trucks...

I have used a plasic angle tool that to me is one of the best bargins going. You can buy these at Sears or any hardware shore. It is a plastic piece that has a manetic wheel in it that when you set it on the york it tells you the degree. The cost about $10.00. Good Luck