Change Bath Tub in old house?

I live in a house built in 1950 The bath tub is 58';x31';x15'; I want to change it but I cant find one the same size This is as big as it can be. can anyone helpChange Bath Tub in old house?
try the inserts all colors, and sizesChange Bath Tub in old house?
The 58 is from sheet rock to sheet rock. If you remove the sheetrock it should be around 60 inches. You will need a sectional with walls or just the tub itself and then do the walls with what you want. Odds are its either cast iron or steel. If your going to do it yourself and its cast, smack that baby with a sledge hammer. It will bust up in small manageable piece. Just be careful cause its as sharp as glass. If its steel, Take it out in one piece or saw it in half. They weigh alot. Its not a easy homeowner job. Good luck
go to thisoldhouse.com
I agree that you are measuring inside the sheetrock. I would also like to add that you can buy bathtub inserts that go directly over your existing tub. You can also refinish and existing tub in any color you want. May be an easier fix that trying to replace it. Try for more info here: http://www.refinishingonline.com/