on my 72 duster, it is 18 in from the firewall to end of sleeve that the cable comes out of. the cable of course, extends out of the sleeve and goes on to the carb. the slant cable would be lionger than a v8 cable as it makes a bend downward and then goes upwards to the carb. hope this helps. my measurement is NOT exact, hard to hold tape when its 18 degrees! LOL
I am looking to use a longer cable than the stock V8 one, as i am going to be using a performer RPM intake. I am going to make a throttle cable mount thats a bit taller than stock to put the cable inline with the carb linkage. I bet if your dimension is for a V8, then a slanty cable might just do it.