nother trans question

Hi guys,
I know I'm the one with the stupid questions, but I've only just started trans building. To those of you who happen to have read my earlier questions: I can't find teh fault, I've checked everything there is in the trans and none of the lines or coolers are blocked. I'l just have to rebuild again from scratch.

But here's another question (probably a stupid one again):
I have an "old" TH700 with a 27 spline stator shaft. Can I convert it to a 30 spline by changing the stator shaft on the pump, converter and the input drum with shaft? Or are internal parts concerned as well and wouldn't that work then?
Just thought those 30 splines might be stronger. Things are breaking in my trans which I have never heard of breaking before although I'm putting it to virtually no abuse at all. Funny. It's my "test" trans, but I want to get the hang of rebuiling those things so they actually work. And I seem not to be able to get all the bugs out. Would be nice if you could help me out again, thanks a lot,
Max