ok ijust destroyed the 203 in my blazer but ihave an empty chevy 205 and a good ford 205 so i was wondering if could put the gears out of the ford 205 in the chevy case  

The case is not the problem here as parts will fit but ford uses a different input spline than GM. You need to match up splines. I would suggest that if your planetary reduction unit is still good that you adapt it to input of the 205 you piece together to give you a 3 speed Tcase. You can find info about this conversion at link below.

http://forum.snoman.com/viewtopic.php?t=166  

thanks snoman appreciate the info