Yes. It will fit (bolt up) just like the DOHC Cobra motor would also "fit".
That depends upon your definition of "issue". Did you have a plan to get the Cobra specific parts to make the swap work?
Have you looked up any threads on Mark 8 swaps as the concept is similar?
Have you priced any Marauder motors? I don't know for certain but I would think they are rare in the salvage yards.
One of the "keys" to make a project like this work is to make the new motor look "electrically" like the original. That means to re-use the original wiring harness and ignition. Some extending of the sensors will be necessary. The GT PCM will run a DHOC with a tune.
For an easier swap consider a Romeo PI from a 2002+ Town Car, Grand Marquis, or Crown Vic. Again it will be necessary to re-use the original wiring harness, fuel induction, and ignition but the parts that you already have will work as is.