Actually the 352 and 390 can have 2 different seals, small and big. Better to just take it with you. If they have to order they can measure it as the book should have the size in there also at napa. Friends 352 had the small and my 390 had large, i would of thought being basically the same engine they would be the same. The only dif was body style, his a 4 door non-XL mine vert XL. I wonder sometimes if they didn't toss in there whatever was on the line, oops buds, we ran out of this one, the line must keep moving so lets toss this in instead! lol
Mine are the big bearings, 390. A friend had a 352 it had small. I think that might be the cutoff for which one it is. Unless the assembly line ran out or something, never know! I try to carry them with me, saves an extra trip sometimes.