Hursty,
I'm pretty sure it's do-able but it's a long time since I had both components in my hand. The Mk 3 Inner cover has what is a blind drilling in the earlier cover drilled right through and an oil seal fitted in the back.
The pawl carrier of course has a splined shaft on the back and is bushed into the outer cover rather than the other way round as previously.
I think that you will just need to blank off the hole for the cross shaft and possibly modify the top hat bush.
The only other difference that springs to mind is that the Mk111 quadrant has a ball instead of a roller but if you're using the early type, it can't make any difference.
Nothing to lose by giving it a try !
