It's a 2 piece seal that fits into the same groove as the rope seal did. If you rotate the seal slightly so the ends of the two pieces don't align with the parting line between the block and the main bearing cap, they seal very well. 1/4" is plenty of offset. A much better fix on the Chevy engines is to machine the back of the block and the main cap for a Chicago Rawhide #38647 full circle lip seal or the equivalent. It solves the rear main bearing seal leak problem for good as long as the main bearing doesn't develop excessive clearance. Since GMC inline sixes have a flywheel flange bigger than the seal surface, the full circle seal can't be used on those engines.
Jerry

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