I was going to put an alcohol injection set up on a bbc I had and tlaked to the tech guys at Ron's because I was told I needed 14:1 to make it work and they said it works better with higher compression but as long as you can get it to 12:1 or so you should be fine. Also should be able to find some off teh shelf pistons to get you the compression you want depending on your combustion chamber size. My first 351 I built I bought some Keith Black pistons that were 12.7:1 with a 58 cc head and they were cheap too.