I have a Ford F-150 4x4 xlt crew cab whit a 4.6 v8. Can a fit a bigger engine and transmission? And about how much woul it cost?

No... if your asking this question you can't afford it... nor can you do it yourself.. sry I'm very blunt.. you'd have to replace your wiring harness ppm engine and mounts . Transmission and modules bcm s will be a problem.. unless you drop a carbed 428 and c6 in it and have a custom shafts made.. then you lose your 4x4. . So no..

Altough it is possible to put different engine and transmission in your truck it is not economically feasible or practical.

To be honest, I'd look around the net and look for something someone already built as a hot rod type truck and purchase it. Secondly, if you state gooses your vehicle every so often for a smog test it probably won't pass.