Timing

I removed the cylinder head from my truck after trying everything to get rid of a P0303. I found my problem was a crack between cylinders two and three. I had another head from my previous truck which was a 1991 ranger. I switched out the cam sprocket with the one from the 1996, replaced the valve seals and installed it on the truck.I double checked the timing, #1 T.D.C. With key way at 12 O'clock and diamond to diamond on the Aux. Gear and cam gear on mark. After reinstalling everything I cannot get it to start. It has the muffle noise when you open the throttle while cranking and sounds as if it's out of time. So Now that I look at the old cam gear I see that the key way and timing marks are in different positions. Do I need to install the 91 gear on it and time it, or is this head not going to work. Thanks.