hornet/american can the suspension be swapped?

Pretty sure the track width is wider on the Hornet.
Meaning adding the Hornet pieces to the American will make the suspension Hornet width.

You'll need to go to a new car heavy on the backspacing type wheel.
Plus all the fitment issues to get the correct geometry on the spring towers.

The crossmembers are the same between the American, Gremlin, Hornet etc...  You would have to change the spring towers for the rest.

Can it be swapped? Yes it can, if you know what you are doing and good with a welder. I have seen a javelin front suspension swapped into a trunion equiped original car, but it required cutting out and installing the Javelin spring tower into the inner fender panel. I just think that the job would be over the head of the average back yard repair men. I think it would be out of my league so the words inexpensive alternative just do not seem to apply.

There's nothing wrong with trunnions. Newly rebuilt ones use poly bushings that will outlast the originals, which typically lasted 30+ years. You can't get but about 3 degrees caster before the bushings bind, but other than that trunnions are as good as ball joints. They are a bit pricey when rebuilding, but cheaper than changing out to something else. If you're doing it just because you don't like the trunnions I'd reconsider. 

That was probably in a Javelin or AMX, but the procedure is the same. I remember seeing the photos... can't find anything about it though. Maybe someone who has done this work will chime in.  In the end, of you have a donor car for the towers and other front suspension components it's not too bad -- if you can weld and wield a spot weld remover, and have lots of time...