I am in the market for an FAL. I am currently looking at the DSA 21" SA5821SP-A. These use a type 1 or 2 aluminum receiver and I am wondering if this is a sacrifice from the treated steel receivers.
Is there any strength difference between a type 1 or 2 aluminum receivers?
Is there an FAL option that takes more abuse?
Is there a manufacturer out there using mil spec parts?

Thanks for any experienced advice on this.

Think like its an AR.

The lower holds the trigger group and mag. Main difference is the Serial Number is on the AR lower vrs the steel FAL upper.

FAL Files might have an answer.  They have a lot to read through.

As mentioned, it is the upper in the FAL that takes all the abuse.   Lower just holds FCG parts (the mag well and catch are also part of the upper receiver).  The reason the FAL uses a steel upper is because the FAL bolt locks against a shoulder milled into the receiver at the rear, as opposed to the AR, which uses lugs that are part of the barrel extension.

If you want a known quality FAL of current manufacture, look no further than DSA.

"mil spec" doesn't really exist for the FAL, since it was never adopted by the USA, but  DSA, FN or Imbel parts are quality.

There is only one manufacturer, and that's DSA.   Coonan and Entreprise still make receivers but not complete rifles.

DSA receivers are NOT NOT NOT aluminum.   Aluminum will not hold up to the FAL pressure.

A great starter gun is the Century L1A1 Sporter with thumbhole stock, typically $600-$700 on GB.   Then you can restore or modify to your heart's content.

DSA rifles are good.  In the current market, though, you may be able to pick up a professionally built gun for even less money.

For some reason, FAL prices are in the toilet.

Lurk around in the "marketplace" at the FALFiles and watch for a STG-58 or Imbel on Imbel to pop up, ask questions and pounce.

EDIT:  This is a cool Argentine rifle.  Here is a nice G1.  I have to say, it seems like a slow market and these prices are just as high as a DSA, on which resale is probably higher.