These cars are pretty much bulletproof. There is nothing major to look for that would cause the engine to fail or transmission to take a dump. Anything that might be a problem can be fixed for cheap (depending on price of part).

On a SRT-6, the main thing to look for at least with my experience is the intercooler pump going causing the blower to heat soak. You'll know if this is the case as you'll have power then bam, it will as if a parachute was pulled and you hit a brick wall as the car will just stop pulling. Other issue is the CPS (crank position sensor) they tend fo fail periodic but nothing major.