What is the difference between black top and silver top rods ( confused)

Need to check on my notes which are at work so cant check til 3rd but there is a difference. Main caps are different too so the blacktop block stiffener (the ally bit) doesn't fit on silvertops.
Water pumps arn't interchangeable either.

Sorry i am after th difference between the con rods.

They use different size big end bolts.

Does that mean they are interchangeable, obviously in sets rather than individually?

Blacktop rods are longer than silvertop and have different wrist pin diameters. St170 rods are longer again.

They all only work when they matched with the corresponding pistons.

I was nearly right, check out the specs here...