Transmissions, the stuff dreams (or nightmares) are made of. For what it is worth, here is my take on your question.
Cost of rebuild - There is little difference between rebuilding a 46RH or 47RH when it comes to the basic parts and modifications. The extra cost you will incur is the converter. Lockup versus fluid coupling, single disk lockup versus multidisk lockup. The hard parts are pretty much interchangeable and the 46RH needs to have the updated parts if you want a decent unit.
Cost of install - This is where you have to spend some more money to get the 47RH installed in place of the 46RH. You need engine adpater plate, flex plate, starter. On a 4X4 you need to modify the lengths of both drive shafts, relocate the shift linkage, and modify the tcase mounting bracket. You will also need a manual switch for TQ lockup or by an electronic controller. If you do all the work yourself the rough cost of the parts is around a $1000. If you hire a decent shop to do the work add another $1000 on top of the parts.
What you have when done -
46RH - With a good fluid coupling and good internal parts you will have a transmission that will take some use and give a good lifetime. A lot of this will be dependent on the builder, the service, and how you drive it. considering the weight you are pulling there a couple things you must do. You must upgrade the planetaries to steel cased ones, you must have the OD setup correctly, you must have correct OD planetary, you must have more trans cooling and closely monitor the temp. If you don't address these basic pieces the trans will work but it will just hammer itself to death in much shorter time.
47RH - The basic transmission contains a lot of the upgraded parts so the internals are fairly strong. The updated OD will take more power and use without grenading. You must updated the OD pinion to the correct one and you must add the needed cooling and monitor temp also to get close to a bullet proof unit. All of the above is also dependent on the builder and their abilities. The converter is where you spend the difference in cost to get what you want/need. Tightness of fluid coupling when unlocked and the ability for the lockup clutch to hold the power and weight you tow are the areas you need to address. Whether you want a single or multi-disk lockup clutch or if you want to use a exhaust brake will determine cost, usability, and efficacy.
The cost of one rebuild can easily offset the cost of upgrading to the newer trans. How you are going to use the truck, how long you intend to keep it, and how much you want to spend are your guidelines.
My advice would be call all 3 vendors (DTT, ATS, Goerands) and talk to them about what you want and how they address the issues. Good luck.
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