NOTE: This is a NEW, GM OEM crankshaft in original crate, wrapped in original preservative.  GM only used 3 PN's in the parts manuals and this number is NOT one of those 3 numbers. In the Mercury Marine Parts lists for each model year, 90 through 95, this PN 10135873 appears.  The indicated vendor is Shardlow (UK) where all of the crankshafts for the LT5 were manufactured for the LT5.  

We are unable to tell whether this crankshaft was factory balanced for the 90~92 heavier piston/pin/rod assembly, or the lighter 93~95 assembly.  It can be balanced for either engine/yeart model. 

Photo shown is not this particular crankshaft.  Stock photo for reference.