I wouldn't keep any other snakes with potential snake eaters. Even if they are too big to swallow, they could constrict and kill them.
Also, Eastern Kings and LA Pines don't overlap in range so it would be a very artificial environment. At least if you had easterns and Northern or Southern Pines it would make sense.
Why not Speckled Kings and LA Pines? They at least overlap in range although their habitat preferences really don't.
I read some research many years ago (I have no idea where) that demonstrated that smelling the odor of Lampropeltis musk made other snakes (I think it was rattlesnakes) behave in a defensive manner.
Do you want your pinesnakes to be under that kind of stress (assuming it is stressful)?
It would be much better to put your male and female Eastern Kings together in one display and your LA Pines the another. Your kings might still eat each other anyway.
Remember, most snakes are not social animals and these animals tend to avoid each other in the wild where possible. Housing them together will probably increase their overall stress levels. Husbandry decisions should be made based on what is in the best interest of the animals, not what would be interesting to us.
Anyway, that's just my opinion on the issue. YMMV. 
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Chris Harrison
San Antonio, Texas