Depends on what you're doing.

In my experience the aluminum heads are great - no issues of note. The lowest cost parts for an FE are the Edelbrocks - we sell bunches of them - and they are basically a MR/CJ level replacement part as delivered. Easily upgraded to serious performance as desired - we CNC port them. Blue Thunder heads will make more power but are likely overkill on a 360/390 based build. The Eds are cheap enough that they're almost better than rebuilding stockers.

Aluminum FE blocks are another deal. They have their place in cars where the 100 lb. reduction in weight is important - like a Cobra for road race work - but they also have their own issues. Cold bearing clearances need to be pretty tight since they grow with heat. Means that a 4WD guy in the Dakotas don't want one if he's planning on playing in the snow and won't fully warm it up first. The cam bearings need to be pinned in place or they will walk out....learned that one the hard way. Head gaskets like to seep fluids unless you glue them up.

Iron blocks will cost less, make a bit more power, keep the threads, and tolerate "bad driver behavior" better.