1978 f100
As you've been told, the bolts are easily obtainable; just get the right size, right thread, and right length. If they are loosening themselves and falling out, do something to help them to stay in place (locking washers, thread lock, etc.)
If you intend to keep the truck and work on it yourself, get a set of Ford Shop Manuals for 1978.
Lots of good people and good info here. Let's see some pictures of your project truck!
(It doesn't matter how bad you might think it looks.... ) start a build thread and you will have a photo log of your restoration.
I have a 1978 F100 also. Mine came from the factory with an inline 6 cylinder engine. Look up the info on your door plate and it will tell you all the original information about your truck when it was made.
Have a good day!

Welcome to FTE, yes you will get good information here. Sometimes that info makes things tougher, but worth it in the long run, That is the case here, as you look for fasteners.
1. Risk of counterfeit fasteners
Hard to believe that people would do this, but it is an issue. Go to the best auto parts store in your area! One of the "old school, old line places"
2. Hardness rating
Grade 8 is about the the hardest grade, that is fairly readily available. I would shoot for that with engine bolts. Grade 5 would probably be ok, but I would not want to go any lower than that. The head of the bolt has markings to indicate the grade. Again, an old line auto parts store can help you here.











