I have a99 expedition, an i was wondering if a 08 crown Vic
engine would fit an run. Without changing computer

 

I would say yes, retaining the computer/expy harness would be better, than having the vic one completely reprogrammed for a expy. From what I know of the 4.6/5.4 swaps, she should fire up and drive fine though you would do yourself a service and invest in a chip and have the computer tuned at a shop that specializes in tuning to have it running 'right'.