You talking about the inside sweep or the outer sweep? If it's inner, some are held on with staples and a specialized dimpling arrangement. Hard to explain but I'm guessing that's not easily duplicated. I know Olds Cutlass are stapled/dimple-crimped. You may be able to get by with short rivets. I seem to recall that's how they did it on my 84
H/O when I had the inner door panels redone. But not sure.
How's your clearances behind the strip? Once installed, the inner seal lip should cover up any rivet heads anyway. Check to see contact areas where the door panel actually touches the door on the top metal strip. That will tell you where NOT to put the rivets.