How does one know which AlClad II to use?

The P-51 was cover with duraluminum.  Alclad make that color.  Use that as a base and then,, with some good ref pics, mask off and spray some of the panels with aluminum, and dark aluminum.  Don't over do it or it will start to look like a patchwork quilt.  Not 100 5 sure what the skin on a Texan was but the above procedure will works on the vast majority on bare metal schemes.

There are only 2 Alclads that require a gloss black under coat.  Chrome and Polished Aluminum.  All others can goo primer that will accept a coat of lacquer.  Alclad is pretty hot stuff and will/can craze bare plastic.

The P-51 (and I believe the AT-6 as well) were covered in Alclad paneling (from which the NMF lacquer derives its name), a corrosion-resistant aluminum sheeting developed by Alcoa in the late '20s. The wings were painted with an aluminum lacquer which as I understand it provided smoother airflow around the laminar wing.

You actually have a lot of variability in which Alclad to choose to represent the Alclad panels. Aluminum, Duraluminum, Polished Aluminum, and Airframe Aluminum would all work, I imagine.

For the wings, I'd consider semi-matte or dull aluminum.

Thanks Guys! Will Mr Surfacer be a good primer for AlClad? Both is lacquer-based right? Doogs, why do you say to paint the wings dull?

Mr. Surfacer should be a good protective layer for the Alclad, but I believe Alclad does best with a smooth, gloss surface so you may want to top it with a clear coat of something.

As for the wings - they were painted with an aluminum lacquer, which is flatter than the alclad paneling. See the difference between the wings and fuselage and stabilizers?

So far as I know, this was unique to the Mustang.

Mr Surfacer 1200 is perfect for Alclad.  It does not have to be glossy.  But is does have to be smooth.  If you can get some 4000 micro mesh, wet sand the Mr. S. 1200 with that.  A coffee filter also does a really good job of buffing the Mr. S. Just make sure you blow the lint off.  The primer will get a bit of a sheen to it but you could skip that step and still get great results with the Alclad .

Aclad makes a gloss black primer that is intended to be used with the Aclad paint line. It is important to aply the metal colors over a smooth surface to avoid "orange peel" texture to you finish. In the past, I tried to skip this way of priming and it resulted in a textured finish....no good on a bare metal aircraft!