Any major brand synthetic lube in the correct weight.
Synthetic ATF +4.
No, it is not recommended. It is allowed though.
SAE 5w20 conventional or synthetic, your choice.
Oil changes are always necessary. If you mean can you mix conventional oil and synthetic, the answer is yes you can.
It is not required. You can use conventional or synthetic oil.
What is the air conditioning oil capcity for a 1999 dodge 1500 with a 5.9
Yes
The oil pan is on the bottom.
15w40 conventional 5w40 synthetic 0w40 synthetic
No.
You can use either conventional or synthetic, your choice.