When searching for runtimes select directory with SOA-P 4.3.0 standalone runtime. It's recognized as AS v.4.3.0 and added to available runtimes during installation. But after installation is finished and JBDS is run this runtime is defined as v. 4.2 runtime and therefore there is a warning displayed in Edit Server Runtime Environment dialog.
When added manually via Preferences > Server Runtime > Environments > Add it's possible to add this runtime as JBoss EAP 4.3 runtime without warning displayed in Edit Server Runtime Environment dialog.