Actually, my search through the FAQ and past related discussions doesn't reveal any bottom end differences between SVT and SE.
Note that by "bottom end" I mean (most) everything below the head: crankshaft, bearings, connecting rods, etc. One notable item: The SVT flywheel is lighter, though I don't necessarily consider this "bottom end", since it can be replaced without opening the crankcase.
The compression ratio between SVT and SE is different, but I believe that's due to head differences, not piston differences. Can anyone confirm this?
Of course, the SVT engine has significant top end differences (heads, intake) and the model gets lots of other upgrades (exhaust, suspension, the list goes on).
Just my $0.02; my original interest in this topic was at one time to verify what was really different between the SVT and my lowly (but fun) GL V6. This is one of the better references on the topic:
SVT vs. SE specs