Hi,
I added both the callaham pickguard shield and the trem-block into my partscaster. The shield did a great job, really pleased with it. The trem-block made a really clear difference, more so than I would have thought. The most noticeable difference was with the guitar unplugged.....everything sounded clearer.
If you follow the link in my signature I kept a blog of the updates I made....it includes more info and some photos on both.
Hope that helps,
Jordan.