This PDF file contains three documents, in order:

• A December 8, 1955 memo to Treasury Secretary George Humphrey from Dan Throop Smith (head of tax policy at Treasury) recounting a meeting that day at the Commerce Department that settled on the outline of the revised highway plan to be submitted to Congress in 1956 (after the previous Eisenhower highway plan was voted down by Congress at the end of the 1955 session). The memo says that at the meeting, Smith urged that “excess receipts in early years be segregated and not considered available as general revenue” which “was accepted and was the apparent intent all along,” which led to Treasury’s suggestion of a trust fund in February 1956. (1 page)
• The plan itself, consisting of 9 bullet points (40,000 miles of Interstate costing $25 billion at a 90-10 match to be completed in 12 years; $9.8 billion in other federal aid over that period; paid for with tax increases of 1.5 cents on gasoline, 5 cents on diesel fuel, up to 5 cents per pound on tires, and a 2 percent sales tax on trucks, buses, trailers and auto parts; no state toll road reimbursement; all on a pay-as-you-build basis). (1 page)
• Notes on Eisenhower’s all-day meeting with Republican Congressional leaders on December 12, 1955, at which the legislators convinced Eisenhower not to mention specifics of financing in his message to Congress, instead only call for “adequate financing provisions” and leave the details to Congress. (7 pages)

Originals located in the Treasury Department Office of Tax Policy Files at the National Archives (Treasury memo) or the Ann Whitman File, Legislative Meeting Series, in the Eisenhower Library.