I would go find a salvage engine 3.4L from a Camaro or Firebird with the least miles.
You will have to add your intake/carb and distributor, would be the easiest swap
and give the best bang for the buck for a performance increase.
You might need a flywheel/flexplate this route if the balance is different.
Sure you can drop a SB in it, but your going to need to fab motor mounts, and find a bellhousing,
maybe even a whole tranny...
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