Hello again,
The two hoses leading to the core are different sizes so one doesn't get them mixed up upon installation.
You would need to go to an auto parts store and get a 3/4" to 5/8" reducer, just tell the guy behind the counter this and what you are attempting to do. And he should be able to get this for you.
Scott
ASE Master Tech/Instructor
20 yrs Experience; GM factory Training ASE Master Certified with L1 advanced engine diagnostics