Front Fenders,Hood fit another truck

This is the truck listed above.

Already took hood off of 1981 F100 before looking this up online. Last picture here is the front of the truck listed above, I forgot to add in the post above.

There's two ways to approach this. The easiest is to visit any salvage yard and have them look up the parts in their "Hollander" Guide. Those are huge and expensive books that will list your truck with every part, and give each of those parts a code number. Next, you look up the code number in the back of the book and it will list every model and year that part is used on.

I use the Rock Auto web site for reference for things like this. You can look up the part in question for one truck, and write down the part number from any of their multiple suppliers. Look up the same part for the other truck. If the same part number is listed, the parts will interchange. If different part numbers are listed, it doesn't necessarily mean they won't interchange. You have to figure out what is different. For example, your fenders might bolt on to the inner fenders, but the creases and body lines might not match those of the doors. There could also have been one or two bolt holes that were moved for some reason between the two years. Other than that, the fenders might be exactly the same, but that difference will warrant a totally different part number.

@Caradiodoc

Thanks, I decided to phone a salvage yard instead of going in person.
They told me the parts will not interchange as individual parts but I could replace the entire front of the 88 with the front end of the 81. Frames are the same and so are all bolt holes.

If they didn't tell you what is different, the parts still might work, but there's a pretty big age difference. Manufacturers make changes every year. Some are insignificant, and some seem to be just so we have to keep more parts in stock or so you have less chance of finding what you need in a salvage yard.

Ive been told this before "If Doors and Hood fit the rest of the body will fit" I believe it's worth a try for the experience alone.

In the 88 the exhaust system is rusted and full of holes. The 81 system (brand new) will switch over but should I change the Factory stock headers on the 88? Also 81 is dual while 88 is single exhaust.

If the engines are the same, the exhaust manifolds are generally dictated by the body and the transmission type. One year the outlet port on one side might be at the rear of the manifold, and for another year it might be in the middle to clear a cross member or something like that. A single exhaust is usually sufficient for all but the biggest engines.