I looked up the Edelbrock linkage you have and it can be hooked up 1:1 (Using the top hole on both carbs) and that will allow each carb to open at the same time, which would be good for a race car. The way you have it setup is a progressive opening where the engine is really running on the rear carb for about the first 1/4 throttle. This is how you would want a street car setup, but you need to adjust the stop on the lower rod when both carbs are at WOT, then at idle the stop on the lower rod will be forward, not touching the bar connecting the bars. This way, only the rear throttle blades open for about 1/4 throttle, then the lower rod stop contacts the bar and open the front carb until both are at WOT at the same time. You can adjust the linkage /stop separate from the throttle cable. Anyhow, make sure you can open the rear carb WOT by hand before messing with the throttle cable. For the throttle cable, there are a few different items to check. First it to make sure the cable bracket geometry will allow the carb to be opened to WOT. If the cable connecting point is in-line between the throttle shaft and bracket before WOT, then the bracket or cable connecting point needs to be changed. The next item is throttle pedal travel (how far the pedal pulls the cable.) You can get a bit more travel by bending the pedal linkage, but that will raise the height of the pedal. The other option is to move the cable connecting point closer to the throttle shaft so smaller pedal travel opens the carb quicker.
I have the older Lokar cable kit, and had to drill the throttle lever to mount the cable further forward and lower.
