Just keep it clean and spray off the undersides when you drive it in sand/salt. Just keeping the undersides clean can go a long way. Also look for rust spots poking through and deal with them fast. If you keep on top of them they won't get bad.

Option two is to spend $2k-$3k on a winter beater.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200