Cat the two files together and it turns into a squashfs filesystem image. Mount that and inside you'll find the usual aerosmith_le-1_02_0.spk
I have a funny feeling that you might not be able to open the spk with Pinball Browser yet.
EDIT: As a side note, it appears Stern are worried about 4GB filesize limits, as the files in the zip seem to be cut at around the 4GB point