Beefing up A500 overdrive

Not crazy power. 318 poly with 4 barrel Edelbrock. Probably about 250BHP 350lb torque. This is within the original spec of the 42RH but I would like to give myself a bit more leeway for freeway use. The car is being set up for comfortable touring but keeping decent performance.

Most of the control setups for retrofit overdrive drop it out on fairly light throttle. The PACT solution with a vacuum switch and 2 pressure switches drops both lockup and overdrive in one go as the vacuum drops which I don't want.
I plan to have the lockup drop out by vacuum on fairly light application of throttle but have the overdrive held on through a microswitch on the linkage. This should mean I can stay in overdrive for relatively gentle overtakes on the freeway and not have a sudden increase in revs.

If I'm rebuilding the transmission anyway it makes sense to me to upgrade at least to 44 spec. if not 46. I wasn't aware of any real down side so please tell me if I have missed something.

I haven't had the transmission apart yet but I'm guessing my 42RH has 2 steels and 3 friction in the overdrive and 8 lined and 7 steels direct. Upping to 46RH spec would be 3 steels and 4 friction overdrive and 10 lined and 9 steel direct.