Lots of reported spring break age with this brand of valve springs.
There are many other brands of springs that are direct drop on replacements
for the Edelbrock E street heads. That have a much better track record.
EG isky 205D or Isky 235D EG lunati 73943 Howards ,,, Even summit racing has 1.26" valve springs for your heads.
Not to mention Edelbrock RPM valve springs.
You can even use cool GM LS6 bee hive style springs with comp 787-16 retainers.
The E street heads will make a lot more power once ported to improve flow.
Now would be the time to do that.