My money is on this trans being out of a 75 and later truck. Measure the front bearing retainer,if it's an overdrive trans,it will measure just over 5" (5.125") to be exact. The shifter bracket on the trans is a factory piece,to get the shifter higher through the truck floor.
Not a good starting point for an A-body. It can be done,but there are alot of variables.
The front shifter pad is for a B-body the rear pad for a E-body. You will need to make a bracket somewhere in between for an A-body. The front pad will hit the cross member when installed. So you either get a BFH and beat a dent in the car for clearance,or grind the pad off the trans. shorter driveshaft,overdrive bellhousing,V8 clutch fork,on and on. It can be done,but get out the Tylenol,cause it will be a headache.On top of that,iMO,will be hoackey.
If a 4spd conversion is what you must have,start with an A-body 833.
Things will go waaaay smoother.