The set up I have is actually a b20 from a 71 140 that had a BW35 automatic. The ring gear had some bad teeth. The flex plate ordered from a salvage yard has 8mm narrow ring gear instead of the 13mm (supposedly original to the setup) from the 140. After measuring the distance from the starter mounting face on the engine block to the front edge of the ring gear they both end up the same distance. The actual flex plate is riveted to the inside center of the ring gear on the 13mm flex plate making the extra thickness toward the torque converter. The crankshaft centering lip only has provision for the flex plate without the spacer ring which is also something I failed to notice before. I guess the narrower ring gear must help in releasing the Bendix after starting because all the later red blocks I have seen has the narrower ring gears. This setup is in my 544 with an AW71 that has worked flawlessly for 12 thousand miles. Thanks for the replies back. Larry