i think you could use the VIN number to figure that out, but not exactly sure.
do you plan on having a mechanic look over the car first? should only be about 100$
he could tell you for certain about the double vanos, but if you do some searching you could find the VIN number that indicates the double vanos(possibly even call dealership and ask)
as for checking if its solid;
-look for rust
-overspray from repairs(indicates accidnet and repair)
-push on all four corners, shouldn't wobble
-let it idle for a while, make sure it doesn't over heat
-drive it, see how it feels, listen to it.
-get under the car and look around.
-bring a friend, second non-biased opinion will HELP you tons
the engine should be a M52TU, and that should be on the engine somewhere, or car.
1987 325i- Daily driver/project