I believe your worst thoughts are true.....three words....rear main seal. Just because it is new really doesn't matter. I know when i replaced mine on my stroker 383, I didn't have to remove the transmission (however it was an automatic--not sure if it makes a difference with a 4spd.--probably not ).
Take a dry rag and a flashlight and look up under the truck while it is idling...with wheels blocked (just in case) and just look all around your oil pan....wipe excess oil off and watch. If it seems to come from around the flywheel, yep, rear main.
If it is your rear main, it only takes a couple of hours, just wear some old clothes because oil will get EVERYWHERE as it drips from the crank. Hint: take oil out of the pan a couple of hours prior to taking pan off.
SgtDel
aka "Andy"
www.delbridge.net
1979 Big 10 383 stroker
1991 Blu 'Burb 3/4 ton 4x4
Edited by: SgtDel at: 11/21/06 11:18 pm