What is the interchangeability of the propshaft on the AQ series drives? I am considering a project to make new shafts that would use the common Mercruiser spline size allowing the use of modern prop technology and the ease of getting a replacement quickly. I just want to know if there were major differences between the 270-280-290 and SP shafts internally. Once it is past the last seal it would be the same dimensions as a Mercruiser outdrive. Thanks in advance Murf