If the heads still have the factory guides, “I” would use k-line bronze guide liners as my first choice.
If they “needed” 1/2” od guides installed, bronze would be my preference.
I use guides with the correct id for the valve stems being used…….so for the parts you’re planning on using, 3/8” id.
Not all shops have the tooling to use all the guide options.
This is why you should be having this conversation with who will be doing the work.
No point showing up with parts they aren’t equipped to deal with.