Would I get a good tone if I throw a Tubescreamer on top of Mark IV lead channel? Any other good advice?
Depends on what you call "good tone". I have been lucky enough to play through a Mark IV, my friends dads friend is a musicians with orgasmic gear, and I found the lead channel to be amazing without anything on it. I supose if you want/need that extra OD and volume it would be nice but honestly I found it to be great as is.
All Hail! The Kala-Kala Chieftain!