That would be the 400 turbo.
Yes - probably a long time ago
There are 6 bolts that holds the transmission to the engine.
YES. The 74 and 86 engine blocks are the same as far as DESIGN.
The 86 2.8L automatic transmission will not bolt up to a 71 Chevy engine.
Depends on mileage, condition, engine, transmission, and options. Click the link.
yes
junk yard
There is only one.
YES.
The transmission oil goes in thru the dipstick tube.
The car has a 700R4 transmission. 4 speed automatic
There is a switch that is opened when the transmission is not in park. If this switch has gone bad, it would cause the problem you discribe. Replace the "Park" switch. Dan