Paul_TC4

I just bought the steel outdrives for my electric TC4. Im doing this as a replacement of the plastic ones because they break on me alot. Now these outdrives are completely different. They are them same size but the lock nut that holds the thrust screw in wont fit in the short outdrive because it doesnt have the mold where it holds it in. What do I use as a lock nut to hold the diff together?

thanks,
Paul