z71 off road cam? lol...that would mean someone had to buy retro-fit roller lifters or had the block drilled for roller lifters...z71 would state a newer model lt1 motor that is roller I highly doubt thats the cam...probably more like a zz4 cam...Do you have the duration, lift, lsa specs of the cam?...What size stall converter is in the truck?...anyways def. trash the heads even if you just go with a set of vortecs...then you would have to change the intake...or even a set of double humps would flow a little better than those...Good luck with the truck! thats a awesome body style to have and they will always be popular.