I believe, sombody correct me if im wrong, but you should be able to take up the slack with a big wheel kit and the amount of adjustment on the rear axle for the 141-144 conversion
I had a 150 Competition A20. It was part of a 'hillclimb kit" and it came with it's own rails. I would not plan on the 150 track fitting on 153 rails. I didn't try it, but recalling the difference in the rails, I don't think it would work.