ford marketing rubbish. i've seen lots of st170 rods and they aren't that strong. i've seen them hanging out of the side of standard power engines

the pistons are normal cast, not pressure cast like cossie or focus rs pistons.

cranks are standard with the addition of a spigot bearing for the 6 speed box.

st170 has 20mm gudgeon pins
blacktop are 19mm
silvertop are 20.63mm
focus rs are 22mm

if you're looking for something to rebuild, silvertop would be easiest as the hydraulics take care of themselves, blacktop you would need to shim up. blacktops are easier to get hold of these days though. st170's are a little more complicated to build due to the vvt and solid buckets, but aren't too different other than that.