No the SRT 4 motors aren't stroked 420A. they're the same motors as the PT Turbos which are basically PT engines (2.4L) beefed up and turbocharged. FYI the 420A isn't the Neon engine, that's the Eclipse engine.

If you're wondering how well the SRT4 will hold up, just look @ the older turbo dodges. W/a lil loving they'll last forever and hold insane amounts of boost (but of course this is yet to be seen)

Here's another video:
http://staff.tcu.edu/jaltschul/SRT-4vsWRX_vs_Talon.WMVWRX vs SRT 4 vs Talon TSi