Doug --
The STEWART pumps have a set screw to add some additional security to the fan hub... and their hubs are billet (on the stage 3 stuff) instead of a machined casting. Either way - I'd make sure you have the big shaft version (3/4" vs 5/8")... or you might get the big shaft again! LOL
You can check your pulley alignment using a straight edge against the pulleys.
Oh... you have that SMALL small block.. :>) -- Actually - I'm thinking of de-stroking mine when I rebuild it. Those little bitty pistons (in mine) just aren't good for a high milage motor..