As KSP 1.0.5 now supports toggling of engine shrouds, the fairingless LV-909 engine bundled with the pack is no longer necessary.

For the next update:

• Change the part category of the engine to an undefined one, so that it is no longer available in the VAB/SPH while maintaining backwards-compatibility with existing vessels

After two or three updates in the future:

• Remove the part completely

Tested 7ed29f2 in KSP 1.0.5 - fairingless engine is no longer listed in VAB/SPH part list, but old crafts using the engine function fine.

This will go into the next release.

EDIT - For reference, here's a list of all the SDHI SMS parts with their corresponding tech nodes: