take a look at this
The question I asked was "what did he recommend to replace a 545 for a street truck.
Glad you asked! I've been saying for years that for performance work it is better to use the older 4 speed auto's than to invest a ridiculous amount of $$$ into the 45 and 545RFE's. I can build a bomb proof 518 with billet shafts, billet converter, etc., with 1000+ hp capacity for what some places charge for a 500HP RFE.
I'm assuming we're talking about primarily street operation with some track time on occasion, with an eye towards keeping full street functionality and daily driving type manners. If we're talking full-on racing or just occasional short street duty, it will require another email!
In my humble opinion, there are two ways to go that are viable and cost friendly.
1) A-518, also known as 46RH. Hydraulic governor 1-3 shifts, Electronic OD and TCC operation as you have mentioned.
There are ways to operate the OD and TCC automatically, either through a kit with switches, sensors, etc., or through a simple hydraulic manifold and two adjustable Hobbs switches off of the governor circuit.
Best benefit of this route is that the A-518 trans can be built brutally strong and I can do darn near anything with them! TransBrakes, Manual VB's, Constant pressure VB's, Non-clutch converters, etc. Once you eliminate the PCM from the equation, there is any number of creative things you can do with these transmissions. In built off-road rigs I can give the ability to lock the converter in any gear, giving the benefits of both automatic and stick transmissions for rock crawlers and dirt racing.
2) 727 with Gear Vendors OD. This route is slightly lighter with a bit less parasitic loss than going with the 518. That's about the only advantage for your application. The basic 727 will not have lock-up capability, but can be modified/built to do so.
When you add up the cost of the transmission and OD unit, you'll be in more $$$$ than going with a 518, which is essentially a 727 with add on OD unit anyway!
Biggest benefit of this route is trans tunnel clearance in older cars not originally equipped with an OD trans. Obviously not your scenario.
Another option (NOT something I recommend being a Mopar guy) is to use a stand alone GM 6L80 and controller. Many toute the strength of the 6L80, which IS pretty strong, but the cost of the trans and controller, bellhousing adapter, flexplate, trans mount, driveshaft modifications, etc., is WAY more money than either the 518 or 727/GV methods.
I wouldn't go this route as I don't see any advantage over the Mopar equipment. If a guy had one laying around for free, and was a good fabricator wanting to do something with all of his spare time, then maybe..
Hope this helps!