With a 555 I would do at least a 1050. 13.5 should be fine on E85 as long as you get a carb that is done CORRECTLY for E85, and keep an eye on the gas % changes you get at different times of the year. I am currently building an E85 1150 to use on the 23˚ SBC in my dragster, however there is a difference with E85 that requires different mods to get the most out of it, set it up wrong and it will not work well. There are only two builders I know of that have a real good handle on it and a lot of test time with E85 specifically, don't expect to put a conversion kit in it and have it work right. You will be spending more money later on to fix it. This goes for any size Holley, not just a Dominator.