Can you buy and use a inner spring that will give you between .015 to .040 or so clearances cold to the bottom lower inner small step on your valve guides?
If so do that I have used those specs on a lot of iron headed motors, both drag race and street and strip with no issues at all Iron heads don't really need spring cups or locator unless you want them.
I do use either a spring cups or spring locators on all my aluminum heads also though
EDITED: You can buy a spring seat and valve guide cutter tool to reduce that lower inner step also
I've had to do that more than once to get the clearances I want down there
Isky and Comp Cams both sell them