Motor is a 1971 307 appers to be leaking alot going to put the dye in and double check everything. If it is the seal looks like Fel Pro makes a single lip , double lip and a off set which would be best ?
Thanx

Single lip is equal to the original equipment of the time. Double lip is a more modern style with the second lip used as additional protection from leakage. The offset seal was developed to counter the problem of rear seal leaks caused by a groove worn in the crankshaft seal area that is too deep for a standard seal to work. The offset seal places the sealing lip in a different positon on the crank seal area and there by avoids the groove and a seal leak. Some "offset" seals have standard seal with a spacer to relocate it and others have the seal and spacer made as one piece with the lip in a different location than original.
As for which is the best, it depends on your situation. I would go with the double lip unless there is a significant groove in the crank, then I would go with the offset. Just make sure the seal area of the crank is clean and free of any other damage or corrosion before installing any seal.
Hope this helps.

Thanx