Hi,
You can use abap based ESS MSS application.
To use the existing applications, you might have to upgrade the Java packages because 7.4 runs on a newer Java engine as compared to older portal installations that ran on Java 1.4 or below
ESS Custom WDJ components migration from 7.0 to 7.4 NW
You can refer this link for migration of application. This might help.
Regards,
Navya.