Hi, 
Swapping engines and need to match crank shaft size to mount Pullys on new engine and canno  find any info on actual size of Tecumsch shaft , Predator : shaft is 00.75"*2.43" keyway is 3/16" and end tapped 5/16-24UNF ? 
First time working on engines so really not sure of best plan to swap, or can i get new Pullys for the new engine ?
 
THANKS 
Paul

Engines being roughly the same HP, vertical / horizontal, I'd suspect the shafts to likely be the same.
 
Worse case scenario, just replace the pulley(s) independently.
 
You can also yank the old pulley and measure that before springing for a new engine
(have a plan in place)..
 
.