I think it's on page 2 of this thread where I discuss the seat base mount. From the photos, you can see that there really wasn't a viable method of mounting to the existing materials. I am willing to bet that there was a different method used in your boat, if not because of the difference between the models, but in the inadequacy of the mounting method in my model year. The method I employed not only provides for a very solid mount, but also allows for base replacement with the removal of 3 hex bolts.
Yep, I had the same hacked out holes from rusted seat bushing that Chap used for some reason! I did, however, have three layers of wood around my seat base holes, so I lagged new big SS screws into new holes. Seems to be holding pretty well so far, this is what I was working with:
