i have a 93 Nissan Hardbody, only running on 2 plugs

i have changed 02 sensor, plugs, wires, cap looke fine,i was told it could be a variety of things, injctors, pulled the bad cylinders ones that arent getting any fuel which by the way is number 2 & 4 plug, they are dry as a whistle, and theres fuel in the injctor, was told could be bad valve or bad head gasket
 
truck shakes bad when idling and shifting out, loses power and slows down on a hill
 
anyone had this problem and maybe no the answer to eliminate fix this, didnt work well fix this blah blah,

I am willing to bet money on it that the head gasket blew between the pistons. I have seen it happen to me more than once. If you fix it and rebuild it, buy brand new head bolts. They stretch when you torque them and they will blow the head gasget again trust me I know from first hand experience. At first, I thought the same as you on the motor. Spent all that money on what I thought was tune up related. To be sure before you tear it apart, get a compression gauge and test it. If it is bad and doesn't hold compression on each of the cylinders, then it's time to tear it down. Hope I helpped lead you in the right direction.