Yes. The only difference between the small block 727 and a big block 727 is the bell housing. Well, there are some internal parts in the Hemi and motor home 727s but as fat as length, they are the same.
A little nugget:
About 2 years ago I converted my 75 440 4 speed Power Wagon to a 727. The transmission was the same length there as well. DRive shafts are the same, transfer case adapter was the same...It was an easy swap.
Too bad you don't want a 4 speed setup. I'd make a really good deal!