You probably won't be able to buy a cable for it off the shelf. There are several issues getting a throttle cable together for something like this. The first thing is the size of the cylinder of metal cast / crimped onto the carb end of the throttle cable. Every different vehicle manufacturer tends to have their own size, and the existing throttle bracket on the carbs set up will be sized for the throttle cable on the motorcycle that the carbs came off of. Secondly there is the end of the cable that goes through the firewall into the throttle pedal (or handle bar throttle on a motocycle). The through firewall part is not common even on Toyota's of similar vintage, the pedal part might be the same on Toyota's but sure to be different on other manufacturers. Obviously it will quite different on a motorcycle. The third issue is the matter of cable length. If the throttle linkage location moves very much you may have length issues. And you have to keep in mind the motor moves sideways (rocking on the motor mounts), so you have to have some slack in the cable or it will break.
So you have a several options:
1. Try to use the stock cable. Obviously this works with the firewall and throttle pedal. I suspect that it will be too short to reach the new farther forward linkage positions on the carb. And the size of the cylinder on the end may not be the right size. If it was smaller you could possibly drill out the linkage, if it's bigger it would be more work to sort out, and would likely require some fabrication.
2. Use the motorcycle cable. This obviously works with the carb linkage. It will probably be too short (a guess on my part) and will not likely not have any firewall detail and probably a different detail on the throttle end. If the length was OK, you might have to modify the throttle pedal in the car and add a firewall mount.
3. Get a cable off another Toyota or another car that has a better length. This may not fit either the carb end or the car end.
4. Get a cable custom made. I don't where you would go to get this done, but there are people that do it.