86 PU w/22R growling

Son was driving his 86 PU and engine started growling.
I started the engine and it sounds like a bag of marbles rolling around inside, it does sound like the upper part (head) but thats just a guess.
I can do the mechanics its figuring out what/where the problem is I'm not at all good at.
my thought was a timing belt/chain slippimg a tooth but I don't know what that would sound like on a 22R
Before I go and tear into the engine I would like some pointers on what to look for in order to determine what the problem is while tearing the engine apart. I don't want to go farther in than necessary as I don't have the time or money right now if it gets to big.
I am aware that its hard to diagnois problems over the phone/internet so feel free to suggest

If it is the TC making the noise, it' slapping against the TC cover and wearing a hole through it.
An easy way to check the TC is to remove the valve cover and yank on it, it's right there in front. If there's a lot of play it's worn and or the guides are broken. You may be able to look down and see the guides using a flashlight.

forgot to mention it was running like crap. Thinking it may have slipped a tooth on the chain or belt, I'm thinking this engine uses both not sure but will find out soon.
The way my luck has been going no telling what it is. I'll start taking it apart soon but not in a hurry as money is thin ang truck isn't needed just wanted. right now I have three vehicles down and I'm thinking the Toyota will be easiest to work on. my Malibu needs a coolant leak fixed (head gasket is my thought) BMW starts running bad after 15-20 minutes. thinking fuel system, sensor or computer, I have a BMW guy for that but he's not available for a while. and I only drive it to the store now so its OK for now.

forgot to mention it was running like crap. Thinking it may have slipped a tooth on the chain or belt, I'm thinking this engine uses both not sure but will find out soon.
...

Uh, it's a Timing Chain, as I said above.

Uh, it's a Timing Chain, as I said above.

is it that much harder to replace if I do it with the engine in the truck?

by removing the radiator it looks like plenty of room but I'm lazy and its more trouble installing the engine and trans by myself, I will probably replace the head gasket just so I can look inside. I know I have a chiltion's somewhere unless my son loaned it to a friend and it never came back, its happened before!!!