Leaf spring left and right, 7 1/4 rearend

So I have a few questions. My son is wanting to replace his sagging leaf springs. 71 valiant, 318/904, 7 1/4 rearend. First question, are leaf springs the same for the 7.25 and the 8.75 dimensionally? I ask because in his research he can't find specific 7.25 springs. They go by year of car and engine. Secondly. I see that there is a left and right side spring. When I swapped the 7.25 to an 8.75 in our big block duster I didnt realize that was the case, and don't remember seeing the even/odd numbers. Sure they were there, just didn't register seeing them. And I wire wheel cleaned them. Do I need to worry if they are wrong. If so do I need to drop the rearend ro check or can I distinguish by one being thicker or anything?