I once had an aluminum carb adapter heli-arc welded to the mounting flange of my stock manifold. I then cut and blended the openings to match the bottom of the new Holly carb. It was a little work but it made a great differance in off idle acceleration. But I used a 350 cfm carb that was meant for a Ford. Less expensive and worked great. Also, i adapted a cable to replace the mechanical linkage.
Would give more detail on how you used cable linkage setup ... cable run, connections, etc. I'm having an Opel manifold modified (similar to what you did) for a Holley 2300 (500cfm). I'm looking to run the cable around the front of the engine (avoid potential problems with acute angles and kinks) ... still haven't worked out the details.