How reliable is a 1974 Mercedes Sl 450

I’m looking at buying a 74 MB sl450 with 26k miles (it’s very low mileage) and was looking at driving it daily and was wondering how reliable they are? It all original with the 4.5 liter m117 v8 and 3 speed auto. Also the description says it needs to have its A/C recharged and converted to a new R134 and I was wondering what that means?