10.5 is what i consider the edge line of a street motor most the time.... still kinda depends on the motor, some street motors came as 11:1..... but a super or turbo would eliminate the 10.5:1 comp.... you really wouldn't want more than 9:1 and thats with a solid motor..... if you plan on a modified intake though, you'll have to run a paxton style blower that sits off to the side like any other accessory but you'll probably have to make your own bracketry unless by the off chance paxton makes a bracket that'll fit your application..... other than that i dont really have much experience with caddie motors except for the 500 i had in my packard