I concur that these are good cards, but can be a bit tricky to work on. Holley now has what you need for the 265 Street Demon. Go here:

http://documents.holley.com/lit701rev10.pdf and download the pdf.

It will guide you through the tuning process. You may find it necessary to go one size leaner on jets and step down one size on the metering rods. If so, you'll need this kit:

https://www.holley.com/products/fuel...its/parts/1921

Have fun!
Glenn