Check out my website! I have picks of the Magnum heads, Gen 1 Viper heads, and the Gen 3 Viper heads! Magnum bolts are 0.51" closer (diagonally) than the Vipers (Gen 3) spacing is the same the Vipers exhaust ports are .2" wider though! That and the Gen 3 heads have 3 to the right 2 to the left bolt pattern and the Magnum's have all 5 pairs to the right. So NO WAY will the factory manifolds fit! Headers could/would with flange modifications.
Hopefully that answered your question!!!