I've also run a 625 Street Demon on the 400 in my Ford truck. I like it. It ran great. My only one complaint was that the primaries ran out too soon and I was into the secondaries a lot. It was because the primaries were so small and this engine has a high demand for fuel in this heavy truck. I now have a 650 DP Brawler on it and it's a beast. I'm sure it could take a 750 Street Demon and I may put one on it eventually, but I already had the 650 Brawler.