What do I need for a good P-38 ?

It's really a lot simpler than the rest of the folks in
RAH would have you believe:

1) Take a couple of big chunks of aluminum and steel.
2) Stick 'em together
3) Mill away everything that doesn't look like a P-38
4) Stick on a few bits of rubber and bakelite
5) Go flying

Dave '1-2-3' Hyde