904 Lockup Transmission Adjustment Help needed

I also have a very similar setup (340--2.76 ratio--but no shift kit). I also would like a larger spread between 3d and lockup. Mine also is about 3 mph. If rdakota340 could tell the scource of a new spring or part #. Or if anyone can say how much to stretch spring that would be appreciated. Does a little make a lot of difference or do you need to stretch it right much? I have heard when people complained there was a service bulletin and different spring that could be installed for later lockup. This was a later service bulletin and not the early production bulletin.