I have one bent valve on a 350.

Can I just replace the one valve and be good to go?

Do I need a machine shop?

Any questions I should be asking in this situation?

 

If one valve is bent there is a good chance that something else also got damaged.
Depending on what damage was done you may or may not need a machine shop, but to do the job properly the the valve and seat should be reground to fit properly with each other (machine shop)
You can only do one valve, but you are talking a chance that when you button everything up you will notice that something else is damaged, and have to redo the job. That is OK, if you enjoy taking the engine apart and putting it back together, but personally I rather be driving the car.
Suggestion, considering the question you are asking, remove the head and take the whole assembly to a good machine shop, ask for a valve job, head resurfacing, and pressure testing.

 

^^^ x2

 

I will take the heads to a shop and have them checked out.
The engine has less than 5k miles since rebuild, but I have it second hand from the guy who had it rebuilt.
It looks so clean inside! Unfortunately there is a missing cam lobe, and the knock is a bad rod, or at least I think it's a bad rod, as I cannot see any marks on any piston face to show any impact, so new short block is in order.

I think I will try to just swap out for another block, and re-use the heads.

How do I find out what head it is? Should there be a casting number on them?

Might want to keep them if they are an upgrade from stock.

The cam is a Comp cam, but the numbers on it say it's for a marine engine.

So it ate a cam, and that's all I can find right now. I would think the metal from the cam lobe would mean the other bearings are no good, which would explain the rod knock too.

 

Be careful when using marine cams, they are designed to run at constant speed and are not very good for road use. Also, some marine cams use reverse rotation for use in dual engine boats, and really don't work in cars.

 

I got it second hand, and I think it's the cause of the demise of this motor.

Someone spent a lot of money on the whole car, and gave up on it when it started knocking.
I am going to rebuild it, and I will probably use an Edelbrock Performer Plus cam.
It already has an Edelbrock Performer intake and Carb on it.
I looked up the Head casting number, 10147898, and it is from a Gen 1 crate motor (I think) so I am going to get the short block rebuilt and re-use the heads.