[pinkpanthernot]

I have a 34 year-old tiled concrete sunken roman tub that's too ratty to even think about soaking in. Besides that, the stopper's gone and the whole thing needs to be updated. It's currently being used as a step-down shower.
Some dimensions: Length 57", Width 27 1/4", Depth 11"(only 6" after I remove the 'lip' upon which the old sliding shower door frame sits).
The center of the drain opening is 9" from the plumbing wall and not quite centered between the two tub walls. There is a small window in the tiled cement block wall opposite the shower doors. I can remove the 'lip' and gain another 5 or so inches in width.
Question: Is there a tub/shower surround that will work in the allotted space?
If so, how can I fill the 6" depth to bring the whole thing to floor level?
And: How will the new tub drain line up with the old opening?
Thanks in advance for your help!
Dave