IMO - A temporary solution could be to remove the preload spring at the trans end (between the bolt block pin thingy and the rod from the bellcrank pivot), looks like that would give you another 1/4 inch of travel adjustment. And/or drill and slot the arm at the carb. Just for reference, here is a pic of my hokey setup I ran for a while. The linkage from the carb to the bellcrank is nothing special, I just used some small block stuff I had lying around and a few random parts. Might be worth a trip to the local wrecking yard to check some stock setups and see if something else would work. I did replace it eventually with the cable setup mentioned.
Oh one other thing, is it me or is the kickdown linkage arm on the trans look like it is installed upside down? (not sure how you could do that)