I'm sure you are right, however I'm not spending the money as an investment. I'm spending it because I believe that it will make the car so much more fun to drive. I've already sunk over $50k into the car. If I were to sell it, I'm sure I could only recoup a portion of that.
The manual trans DOES make the car more fun to drive. I did the TKO 600 swap in my '70 Charger and even there, I had to cut and build a "doghouse" to make room.
Why didn't you do this job yourself?