Depends on your bell housing.
The 3 spd.and 4 spd have different bolt patterns.
There's 3 bell housings. One ea. dedicated for ea. tranny and there was a dual pattern bell housing.
The dual pattern may be a /6 ONLY bell housing but I am not sure.
I wouldn't think you would have the dual pattern bell housing on your poly SB.
Regardless, grab that tranny.
We'll figure out later on how to get it to mate.
ALSO, on the 4 speeds, there are several sizes of bearing retainers so that will affect whether or not it will bolt up to any particular bell housing. Retainers can usually be swapped out or machined, though.
In summary, Doubtful.