Milviz already started to sell their P-38 Lightning in different packages solutions according to your needs, whether you fly in FSX/FSX:SE or P3D v2 skies.

For each simulator, you can either purchase the complete version including TacPack to get functional armaments, or just the standard and cheaper standard version which already gets animated and releasable armaments and fuel tanks at least. Just note that TacPack copy is not included, so you have to get it directly from Vertical Reality Software, and that TackPack won’t work in FSX Steam Edition.