Seventies Impala gets new tires… only some?

First of all a friendly HALLO to all here in the US round. I bought myself a 1977 Chevrolet Impala station some time ago and am about to beautify it or put it back in an acceptable original condition. It will certainly open up in the future the one or other question, how exactly the situation with the exhaust system behaves… but to that when it is time. At the moment I have a tire problem. At the moment Cragar Wheels are under the car I already got a set of original steel rims (15″x7″ and got me a set of old wheel caps. Now I want to have the right rubber on it. My main problem at the moment is that the car has been running in Holland so far, so I don’t have the permitted wheel/tire combinations in the papers anywhere. So far this is derivable, if I have the original rims, however I have I don’t know if my speedometer still shows correctly if I raise 185/65/15 88H. I know that 185mm is wider than the 178,8mm (7″ of my rim). Does anyone have any experience with it? I found the size in particular because I was looking for all-year tires with white wall ring and the selection is not necessarily infinite and I found it in the e-bay. I am hopeful that someone can help me to finish the conversion soon. Best regards from the West, Hank!