I would use the new rings and the old hats.
Put the o-rings on the injectors. If they are tight on the injector body, and can't easily be turned around or moved, that's step one.
Insert an injector into the lower manifold. If it is very snug, and does not pull out easily, and isn't able to be turned easily, then that is step two, and the o-rings are probably fine.
I usually have to put a little motor oil or petroleum jelly on the injector o-ring to get them to go into the lower manifold more easily, without binding or twisting the o-rings.
You can easily install the injectors and fuel rail into the lower manifold, bolt down the rail, and cycle the ignition several times (WITHOUT starting the engine) to see if there are any fuel leaks under pressure. If, after several key cycles, everything is dry - proceed to install the upper manifold and finish the job.
Put the o-rings on the injectors. If they are tight on the injector body, and can't easily be turned around or moved, that's step one.
Insert an injector into the lower manifold. If it is very snug, and does not pull out easily, and isn't able to be turned easily, then that is step two, and the o-rings are probably fine.
I usually have to put a little motor oil or petroleum jelly on the injector o-ring to get them to go into the lower manifold more easily, without binding or twisting the o-rings.
You can easily install the injectors and fuel rail into the lower manifold, bolt down the rail, and cycle the ignition several times (WITHOUT starting the engine) to see if there are any fuel leaks under pressure. If, after several key cycles, everything is dry - proceed to install the upper manifold and finish the job.