Here is a snapshot of your engine indicating the reason for your poor lowspeed performance; notice the VP of 82
Static compression ratio of 8.5:1.
Your dynamic compression ratio is 6.77:1 .
Your dynamic cranking pr.essure is 128.43 PSI.
V/P (Volume to Pressure Index) is 82
If I recall correctly that 69 -318 already has closed chamber heads.and so, with a TRUE
Static compression ratio of 9.2:1.
Your dynamic compression ratio is 7.68:1 .
Your dynamic cranking pressure is 151.60 PSI.
V/P (Volume to Pressure Index) is 118
This is a low-rpm improvement of 118/82=plus 44%
Now that's with a true 9.2 Scr
To give you an idea of what this means, imagine your engine just got 44% more torque at about 1800 rpm. This is a huge improvement, also akin to increasing the rear gear by 44%..
Now, changing the ICA to 108 will really mess up your overlap period and wreck the whole point of having that cam, which is the 72* of overlap, which, with properly working headers. will make a nice little power boost somewhere around 5200/5400 rpm. With a 108 install, tour intake will now be opening at 8* sooner and the exhaust closes 8 degrees later