I would tap it out as good as possible and ask for 75%. Those kind of dents if you can get behind with a block of wood tap out pretty good. That dent will cost your resale 5-800 so 75% is reasonable.

Oh, and I would replace the pair of front tires. Always replace in pairs.

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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