I have an 1987 G body car with a blown engine that I want to get running again.  It has sat for 20 years, often outside and some in an old shed.  Im in the south east US. Im thinking about getting a cheap used v8 engine to replace the blown one but was wondering if the transmission would need repair. It worked perfect prior to being parked, but after sitting unused for 20 years Im afraid the transmission will fail quickly, or just not work at all.  This concern changes how I move forward with this project. If the transmission would function good for a couple of years, then I would later on replace or build it up in order to start an engine build once I save more cash.   If the transmission has toasted itself by sitting, then my plan might include an LS engine and tranny swap right now, or wait a couple of years then do the LS swap.

My desire was to get the car rolling again very cheap and be able to use it as a go to and from work car while I pass my current running vehicles down to my kids. Then be able to build the car into a fun street car later.  Any advice or experience with an old sitting transmission?