I have never had to go back to check my cam journal bolts but, ONCE, I changed out a cam without replacing the HG. Drain the coolant, pull the spark plugs, and cross your fingers.
You have the timing cover bolt, the weight of everything attached to the head, and the gasket "stick" hopefully holding it on till you get the cam in. I also stuck some bolts back in with spacers to hold things in place so I didn't knock it loose.
I only did it because I was in a bind. If I had heard or saw that the head broke loose, I wouldn't have continued.