Were those the Todd Marsh Sidewinders?
When I was researching building the GTX motor, I looked at my options. I liked the Sidewinders - yes they are a knock off head but the casting looked quite a bit better than the Eldebrocks I have seen. The casting looked real good. At that time I was not aware of the TrickFlow heads. I wanted to stay with standard port heads/intake and I felt that these heads would easily make my goal of 650 hp - fully ported.
Well my goal changed to 700 hp, and it would need to be too racey of a motor to get 700 hp out of these heads so I went with the TrickFlow 270 heads with a Mopar 337 intake. That met my 700 hp goal (results were 713 hp at 6000 rpm and 707 ft/lbs torque at 4600 rpm).
The one thing with the Sidewinders is they have a large chamber. That makes it tough sometimes to match for compression. My fresh spare motor would actually work very well with these heads (about 10:1 compression) and I should probably just save them for this motor. I have no plans for the spare motor right now.