Go for it! I think most of them rattle like that. Expect 20 mpg. Anything over that is a bonus. If you are going to drive in Michigan salt invest in POR 15 and wash it daily, or it will look like the rest of them up here in no time.

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1959 Gravely LI, 1963 Gravely L8, 1973 Gravely C12
1982 380SL
1978 450 SEL 6.9 euro restoration at 63% and climbing
1987 300 D
2005 CDI European Delivery
2006 CDI Handed down to daughter
2007 GL CDI. Wifes