not to say that it can't be done. but the GM trannys have much different mount points than a ford , one of the reasons why it so convienient to swap a 5.0l t-5 is that the tranny mount is basically the same and there are several companies that make a crossmember to swap it. what you can do and would probably be easier is to find a good ford t-5 case even a 4 or 6 cly and swap the GM guts into it. this is of course if the GM trans is out of a V8 car and is up to the task.
I don't think that there are different mounting points. The bellhousing might be different, but the transmission itself should have the same casing. One thing I am sure on is that the GM trannys where weaker then the Ford, so if you do put a GM tranny (cant really call it that though, they were all made by BW) then not expect it to take any kind of power.
The earlier GM T5's have a different mounting points to the bellhousing. The later model ones have the same as the FORD, from what I have seen. Another problem you will have is the input shaft depth is incorrect for the Fords, spline count is different on both the input and the output shaft, so another yoke will be needed.
Sell the GM T5 and buy a Ford Unit. You will be happier in the long run.