engine mounted - no problems - clutch assembly needed another shim to snug up the bell -- exhaust hub on the.28 is big no way using the provided seal the header will fit not  - using the original engine seal - no good - used 2 -- O - rings - 0.5 od .375 id by 0.060 -fits like a glove  - will the O rings last ? - have no idea until the truck  has been fired up -