Cam before heads

Thanks for the replies. I could replace the springs without removing the heads, I think I have the adapter for my air hose to keep the valves closed while I replace the springs.

I would then have to remove them to get the new heads ready putting the car out of commission for awhile.

I may just buy all the parts, build the heads and assemble the components at one time. The last thing I want is to ruin the engine because a valve spring broke.