LA Block/Magnum Heads

You know about using AMC lifters , as you will be using push rod oiling with the Magnums....right ?
Different pushrods too.
I am not sure a solid roller is worth the extra expense here either.
If I did go that way , I'd probably lean towards a hyd. roller.
With a solid roller , you will find the limitations of the heads pretty quickly.
I get the impression that you are taking low mile pieces with the intent of running them as is ?
If that is the case , I'd run a nice hydraulic cam ( flat tappet ) and enjoy it.
Getting around 400 h.p. should be doable with this direction.