Okay, I will try and answer your questions in order. I have changed cams in my 5.7 Eagle 2012 R/T Classic 6 spd. twice now, the first time to the 392(6.4) non MDS cam and the second to a larger custom cam for more power. The 392 cam was the better all around cam, the custom cam was good for more power over 4000 rpm's with a little lose under.
1. If you have a non MDS 5.7 engine then you need the 392(6.4) non MDS cam part# 05037379BC
2. The valve springs NEED TO BE REPLACED, the 5.7 Eagle springs are good to about .550 lift the 392 cam(6.4) has .571 lift, can you say coil bind. The 392(6.4) springs will not work either on the 5.7 Eagle heads, Mopar Performance makes a performance valve spring kit for the Gen 4 VVT engines, the part# is P5160074 for up to .625 lift.
3. Yes, and as I stated in reply #3 above, do not lock out or use a limiter or you will lose power with this cam. It was engineered to give best performance with the full cam timing sweep. If you use the stock 5.7 Eagle car intake manifold this cam will pull hard to 6000 rpm's, put the 6.4 SRV (short runner valve) intake on it and hook up the short runner valve mode electronics and it will pull hard to 6400 to 6500 rpm's and make more low end torque in long runner mode, if you go this route contact me and I will tell you how to hook the valve up with and MSD 8969 RPM window switch. The 5.7 truck SRV intake will not fit on your 71 Charger, not enough hood clearance.
P.S. These 5.7 Eagle Hemi's love long tube headers. wakes them up from idle to max rpm's
