4.8 vs 5.3

I have heard that they are the same block which is the 327 i belive. is this true. if so could i change the intake and the heads and get a 5.3 harness and it work. Anything i can do to increase the hp. ii have a friend that has a 5.4 in f150 and it as 300 hp and i have 285. i want to have more horspower. also i found out mine has more room in the extended cab and is kind of bigger over haul gotta love chevys.