440 in a body radiator

I noticed there are 26 and 22 in wide rads, where do you measure from? The core or the mounting bolt holes. I have plenty of room on either side of the 6 radiator. Just been out of this so long that I forgot more than I knew. Just retired from USAF after 25 yrs. This car is kind of a get out of the house and do something project away from the wife. Bought it for my daughter, but she wanted to paint it blue, she now drives a Saturn.