I have a viper t56 in my B.B. duster for 7-8 years. It’s great. I really like having overdrive. Between that swap and when I put the 700r4 in my Jeep wagoner I found I was driving them much more.
I didn’t buy a kit, a guy or 2 did the t56 on bigblockdart forum. I wanted overdrive, at the time a used t56 and QuickTime bell seemed like the cheapest possible overdrive option.
The 2 overdrives seems useless to me. Maybe it works good in a modern oem efi vehicle but it doesn’t seem to be necessary with an old B.B. I’m running 3.73 with a 25.5” tire. I can go with more gear but it seems like 1st gear would be useless then. Maybe it’s me or where I live but I’m not really cruising faster than 75mph.

I saw that g force modified mustang trans in one of the magazines recently, 5 speed with a 1,000hp rating that seems really interesting. Looks smaller too. I would consider that next time. Mph and speed are close to hemijoel, I have to be doing 70 to use 6th. My engine will still pull at 1500rpm but you can just feel it wants to be at 2,000 under that kind of load.
If the gforce will fit with minimal floor mods it seems like a winner. I just haven’t seen anyone running one in a Mopar.