VX V6 autos will cut a low 7 on a Gtech no problem at all, VT's aren't much slower and in fact all of them run about the same time (good ones). You can make any of the V6 in executive form go about 6.9 with minimal mods. But after that your pretty much up against the wall. The 5 litre is similar but you are fighting against 5.9 rather than 6.9