After some minor research, you will have to purchase Type III Body Armor or higher to stop a high power rifle round.

Type I armor provides multiple-hit protection against .38 Special RN lead bullets and .22 LRHV lead bullets.
Type II–A armor provides multiple-hit protection against .357 Magnum JSP bullets and 9 mm FMJ bullets.
Type II armor provides multiple-hit protection against higher velocity .357 Magnum JSP bullets and
9 mm FMJ bullets.
Type III–A armor provides multiple-hit protection against .44 Magnum lead SWC gas checked bullets and
9 mm FMJ bullets.
Type III armor provides multiple-hit protection against 7.62 mm (308 Winchester) FMJ bullets.
Type IV armor provides at least single-hit protection against 30–06 AP bullets.

When you get into the higher classes of body armor, it gets VERY costly. They use the Kevlar material but also use a series of either metal or ceramic plates over the vulnerable organs, ie heart, lungs etc...

As far as head shots go, you are SOL. I could be wrong, but I don't think there is a helmet made that will stop a high powered round.

Sorry if this is too far off topic, it is just a subject that I have much interest in. I tend to get a little carried away

Ox

p.s. Very nice truck RockPick