are the engines on a 2004 the same as the 2004 Crown Victoria

Are you talking a 4.6L engine or a 5.0L engine? Typically the Mustang engines differed from the Crown Vic (with the exception of police models) in that the Mustangs used a HO (high output) 5.0 and the Crown Vic/Grand Marq/Town Car used a regular 5.0. This entailed a slightly different firing order and other small differences. That said, the blocks should mount up the same, but there may be slight issues with positioning of bolt-on engine components in the different vehicles' engine bays. In the newer cars there may also be PCM issues such as tuning the Crown Vic to use the Mustang HO engine, or problems with sensors not calibrated for the different outputs.

ford stopped putting the 5.0 in mustangs in around 96. if its an 04 gt then its a 4.6 and the crown vic has the same engine that year its roughly the same setup as well

I have a Crown Vic and am very active in the Crown Vic community. There is no difference whatsoever between the Crown Vic 4.6 and the Mustang 4.6. The Crown Vic actually had the 4.6 installed first in 1992 and subsequent generations of it migrated to the Mustang as well. Also of note is that the 4.6 from the F-150, Expedition, Navigator, Town Car and Grand Marquis is also the identical engine in the cars and the same block in the trucks. So yes you can drop and F-150 engine in your mustang with minimal issues.

Yes-It"s as simple,as that...