Even if you keep the stock cam, the timing chain tensioner and valve springs(you can use stock 6.1 springs) should be replaced. On HorsePowerTV they took a boneyard 5.7 and rebuilt it with elect water pump($700!) and FAST EZEFI ($2000+), headers, stock cam with new rings, bearings and dyno'd 400 HP 400 ft lbs tq

Oh, I forgot about replacing the MDS lifers and solonoids. Another 150-300 bones

The 09 Eagle heads can not be used in stock form on the 03-08 5.7 short blocks because of thier 66cc chambers vs. the 08's 84cc. Inertia has Eagle heads with enlarged chambers that yield 10.75 + compression ratio on the 08 down short block. Otherwise those heads will have like 12.5:1 CR!

If you are a glutton for punishment, like me, Nothing Beats the Cool Factor of a Modern Powerplant. But, you have to think out every detail and do your home work to make it work and not waste money.

I say go Gen III Hemi. How many 1st gen Challengers have big blocks? 90%?