Okay, I'm at my wits end. Had to just call it a night.
73 Duster, old 318 car, I'm swapped a 360 made into a Stroker.
P/S, 904. Spool mount set up. Swapping in Motor, and Transmission together.

Me and some buddies worked the engine down into the car..the passenger header was giving me a lot of issues laying loose in the engine bay, so I just pulled it out, and dropped it in..both spool motor mounts seated, and their washers where they should be. the transmission mount likewise, get it into place and it bolts right in. I leave the motor mounts in front loose, so I can bump motor up and slip header in that way on the pass side.

I jack car up. and use engine hoist to raise engine. No problem, I slip header in from underneath. had to take oil filter off but it made the area it needed to be in. well for it to bolt up, engine needs to drop back down.

i take car off jack while buddy aids the engine hoist so they are evenly let down. i get car down, he gets hoist where it is about to set engine in the k frame.

Then it happened, the drivers side spool slipped right in, and the passenger side...didn't. its bolt rests just above the k frame mount. You can push and push..no recoil, it's jammed there, and funny thing it, the mount and spool looks like they should just fall together. Both headers are loose..you can rattle them around, the steering clears everything. the oil pan clears everything. the starter, clears everything. in fact I am frustrated it was just in place and a simple lift to one side won't let it seat.

Going to have another look tomorrow..any suggestions in the meantime? thanks..