can anyone tell me if I can use a mid 80s slant six in place of my original 66 without a lot of changes?,thanks in advance!!

Yes, a later SL6 can be swapped into a 66
You will need to change oil pans and oil pick-up tube.
You will also need to add an adaptor ring to the back if the crank and use the later flex plate.
All the other needed parts from the 66 engine will swap over.
DD

I need a valve cover from a 81 slant six head

_________________
Mopar or Nocar But my wife drives GM