first off, the SRT8 models come equipped with a 6.1L, 425hp engine, while the 300C comes with a 5.7L, 345hp engine. also, the SRT8 models come with upgraded braking systems, suspension, wheels, body, etc...

as for a hemi truck build, check out www.DodgeForum.com . There are tons of guys there who are running modified hemi rams, from mildly modded to heavily modded.