I bought the 4" lift from Rough Country.All new springs.Some dont like Rough Country but was very cheap compared to other companies.Around $625 for 4 springs,4 shocks,hardware,and bushings.I dont think they make a lift for 67-68s but Im not sure.Here is a link to their site.I bought my kit off ebay.If you are intersted in that link let me know.
http://roughcountry.com