Started to leave home,van cut off. I've replaced crank sens ignition mod and dis

Run fine,if I ran 65 or faster check guage light flicker ,and temp gauge would start to jump,then when light would come on all the way,temp gauge would peg. If I let off gas temp gauge would go back to normal instantly

5.7- had issues of it not wanting to stay running when I first bought it,but I'd hold brake and gas,get it rolling,then it