If you can get them to the bottom or top coils, they will minimizes the issue Jerry talks about above. For a short term fix, it should be OK for a while, but I would shop for new springs as money becomes available. Original springs surely have lost some hight over the years, so new ones just may bring it up to the hight you want with out spacers.
If you can find the type that go under the springs, the spring rates will stay as they are and you will gain hight with out any issues.
https://www.budzter.com/spacers.htmlhttp://www.summitracing.com/search/Department/Chassis-Suspension/Part-Type/Coil-Spring-Spacers/Year/1965/?Ns=Rank%7cAsc
Summit Racing has a bunch to choose from. We have used the aluminums that set under the springs with good results.
Joe