Well, given the whole breadth of the project, that actual throttle linkage isn't really the top concern.

You could modify the existing pedal fairly easily to use a cable. Remove the rod that goes from left to right. Twist it so instead of poking into the engine bay it stays inside and points striaght up. Modify it so it will hold a cable. Drill a hole in the firewall for the cable housing.

I'll probably do somehitn similar when I go from DCOE's to ITB's. My existing linkage is similar to the original, except the throttle shaft is attached to the manifold at two points instead of one, and not attached to the firewall. A push linkage drops down from that to the original location down by the bellhousing. There is a slight bit of feedback from engine movement into the throttle, I'd like to get rid of that. The 164 motor mounts help, but a cable would eliminate it.

Even easier (possibly) to just get a standalone gas pedal with attached cable and mount it to the floorboards, take the original out completely.

Oh, and I forgot. In my little parts pile I have a weird little linkage from a '72 automatic 145E. It hooks to the firewall on the mounts for the SU throttle linkages, and attaches to a carb-style pedal linakge poking out near the bellhousing. It has a fitting for a cable on it. Slightly klugey looking, but 'factory'! I think modifying the pedal shaft would be cleaner - that's how but my 1800E's were arranged.
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I'm JohnMc, and I approved this message.