It is a Hayward number sp 14xx I think. Right now I am drawing a blank. You will have to dig up the plumbing under the deck to put these in.
Thanks for the tip with a little more specifics on the return fitting.
As far as digging up concrete, in order to replace return plumbing that's something that I won't be doing - new liner or not. My fiberglass is holding water nicely, and will continue to - either way. Though I may have to come up with a custom round flange or faceplate.
If you think about it, in its' most basic form a liner would just at a 28 mill new pool interior surface. A new gel coat (though controversial in terms of longevity) would also add something like another 10-15 mill coating to the inside surface. Since the fiberglass holds water, if I can find a return fitting which works with the current plumbing and the vinyl I'll use it. Otherwise I plan to trim neatly around each return and generously silicone the vinyl to the pool wall around the returns - possibly adding a custom round flange ring and gasket screwed to the wall With the main drain I'll do the same thing except there I will also remove the grill, trim out the opening, silicone vinyl to the fiberglass, and re-attach the grill. Update... one liner expert says silicone may not last in chlorinated water! (if true, I may have to find an alternative)
Like the plan with the returns, one liner manufacturers suggests that the blunt end of the liner which will terminate at the steps, be Siliconed there to the pool wall on either side and base of the steps, and terminated with a custom face plate material. A similar technique is apparently used when free standing plastic steps by Quaker Plastics are incorporated into a liner pool. In that case, Quaker makes a proprietary track which extends around the perimeter of the face and vertical sides of the steps when it meets the liner and that track has a gasket and seals it. It's applied with ss screws.
Without covering the steps at the shallow end, I can do this for about $450, so it seems I have little to loose and lots to gain...potentially.
I'd really appreciate hearing from anyone with experience retrofiting concrete or fiberglass pools with liners! I will be mostly swayed by any actual field reports, because there just has to be real world experience out there which could benefit many of us!