IIRC the measurements are the ones given in Genesis. They’re in there for a reason.
There isn’t any way to know what a cubit was unless the person that did the measurements left behind some artifact that we can measure now. Sure, we can all read the numeric specifications in the Bible. Unless there is some way to have an equivalent in our measure, we cannot look at anything and say, “Look! That is exactly 300 cubits long”. As it now stands, I could declare the Empire State Building to be exactly 300 cubits tall while you could declare the length of a Viking longboat to be exactly 300 cubits long.