Remember, Good heads don't need much cam to make hp, poor flowing small heads like the 305 heads needs more cam to make the same hp. Cams can crutch a head to an extent. If you go 268, use the Lunati Voodoo line. According to UD Harold, the designer, it made 25hp more than the comp in back to back test on the same dyno with just a cam swap. 268 or 274 on a 110 LSA will run vacuum accessories fine. I am running a 278 roller on a 108 LSA and pull 11" at idle. It would be higher on a 110 LSA. My vac accessories work fine.