Fix Up? or Sell?

[AEeighty-six]

i just bought a 1985 AE86 SR5 stock for $1200us.

the odometer reads over 300,xxx mi. and doesn't work.
the spedometer doesn't work. worked when test drove. cluster is okay. unsure of the problem.
the driver's door sags on its hinges. has to be pulled up/out to open and slammed shut to close.
the driver's side view mirror is taped on. and the mirror just fell off.
can't find the needed Air Cleaner Hose, No.2 and Clamp for smog.

those are the problems...

of course i want to fix it up.
what i want to do is...

4a-ge 16v swap. from a 4a-c.
rear disc brakes. from drum brakes.
lsd. has no lsd.

would it be worth the money to fix up?
or just sell the car, save myself from trouble, and get a GT-S?