A500/A518 to Gen-III

Are you planning DBW or DBC?

If you are doing DBW just use your throttle cable hooked up to normal linkage that is not hooked to carb.

I thought I saw someone just drill a hole in a DBW pedal and run a cable thru it.

There are solutions out there to make whatever you are doing easy. Thankfully lots of dudes have done the swap.
Mine will be DBW. I thought I saw were someone did that. Generic cable from the transmission to a throttle body. They just clamped the generic wire on to the TB cable....