'74's were the most desireable of the mid years, and with the motor transplant on your car, the 2.7 liter faults go away.
If this car is sharp, rust free, drives nice and presents very well, you could probably see $15,000, less the cost of the trans rebuild (which seems to run $3500 to $5000). Again, if it's nice, I bet you could fetch $12,000 for it as it sits, maybe more depending on how bad 2nd gear is.
Good luck!
Jay
90 964, 84 3.2