the 8 1/4 is large bolt pattern. make sure it has decent gears in it. don't want to be stuck with a 2.45 gear. if its a 3.23 sure grip then go for it..
personally i'd spend the extra and go with the 8 3/4. when you are ready for a better set of gears and a sure grip ya just change the center section..
both you'll have to shorten the drive shaft for anyway.