There are mixed reviews on the 7260's, they are a lot stronger than people think. I have friends that abuse the crap out of them and have not broke one ever with 700-800HP leaving on the brake and NOS.
As you can see I am going Ford 9", At that time YES I will be going with 1350's. I did this on the other 9" I set up for my other car. 35 spline and spool. It was cheaper now for me to run what I have then switching out the pinion & Trans yoke for the 8 3/4 when I am making the switch to the 9".
Where did you get your Input Shaft set up?
I thought your car was a Big Block? You are running a 904?