GE used to make a Stirling engine called the ST-5. It was aimed partially at a 3rd world market, though it had applications in the United States as well.
If I recall correctly it was not a commercial success. It could generate up to 5hp under ideal conditions, but the device was expensive. Again, if memory serves, it was too expensive for the 3rd world market and underpowered for the domestic market. I did find an online manual for one HERE:
This might be interesting if you could find one used or might make a useful template if you decide to build one. Frankly, I would love to see someone actually build a practical Stirling engine as despite their promise, relatively few have been built.