Paxtoned 416 won t fire with lid on when engine is cool

IDK anything about this set-up, but I do know that in order for the fuel to come out of the fuel circuits, there has to be more pressure in the bowl than at the butterfly. So I'm wondering if your throttle valves are open too far and the cranking is pulling air around the throttle valve with no fuel being delivered to the transfer ports.If you have a working choke and fast idle system this might not apply. But it remains that the float-bowl vent has to see at least atmospheric pressure at start-up.

Usually the PCV is the idle-air bypass, so you can close the throttles more. With a super, IDK how you would run a PCV. And if you end up not running one,then for sure your T-port sync will be off, and very likely the butterflies will be open too far.
Try closing your speed screw a couple of turns and see if it likes that. If yes, then you will have to figure out how to make it idle lol.
You might need what they call, a throttle kicker.