+1 for seals direct - not the cheapest but the quality is superb. If you're unsure on what to get, take a picture and they'll advise on what's required.
Assuming you mean the rubber u- shaped seal between the high top and the 'tin top I got rid of mine way back. There were rivets to hold the high top on to the tin top but these were just rust spots/holes and muck used to collect behind the rubber.
Removed trim & muck, treated rust, squirted rust inhibitor into holes and filled with Isopon. Squeezed Sika adhesive/filler into joint/space between high top and roof. Front and rear treated the same. Been like this for 10+ years.