To adapt from 16v to 20v extractor flanges the commonest way would be to increase the flange outwards on the two extreme edges with the same material and re-drill the flange. A different less preferable solution would be to shave the outer edges with the flange and after that use https://4age20vturboengineforsale34110.alltdesign.com/details-fiction-and-blacktop-4age-for-sale-49213284