[Mike C]

What size wheels and tires are on the truck? My '69 was WAY higher than that when it was stock FWIW. My opinion is that your truck has lowering springs on it already.

My next step would be spindles in front and block in the back to see where it winds up. Then look at dozens of pics of everyone else's truck to figure out what rear spring you might want to get. But 5" spring/ 2" block should let you get it down without having to c-notch.