I am trying to replace a tub that was installed in 1970 in a concrete floor. I was hoping to install a shower pan that was designed as a tub replacement. It is 59 7/8 inches X 32 inches. After I removed the tub, and reading other posts, I realized that I would need a 2 inch drain. The problem I have is the existing drain doesn't even have 1 1/2 inch, looks more like 1 1/4 inch, or it is a part of some tailpiece/slip joint that has been concreted in. I have included a picture, the tub drain/overflow assembly was just sitting over the little pipe concreted into steel trap, it was a nice fit. I have resigned myself to the fact that I cannot install a shower unless against code (live in Ottawa, Canada) and I'm not sure I can install a tub without replacing this little 1 1/4" stub.
Please, please help. I was living in Alberta with my university student son when my wife bought this house in Ontario - told me it would require a LITTLE fixing up... sorry, trying to get a picture attached.

C:\Users\Damian\Desktop\Lower Bath\img_4093.jpg

Can't post a picture? I discovered that the little 1 1/4 inch stub cemented into the steel flange going into the concrete looks exactly like a little 3" long tailpiece from a sink of some sort. This little brass pipe sticking up about 1 inch from the steel/concrete was wrapped in tape and jammed into the bottom of a brass T which went to the drain of tub and overflow.
None of this sounds right to me. Even if there was a nut put on like a compression fitting, which there wasn't - it would be upside down compared to a sink tailpiece. Couple questions: How would you normally transition from steel to ABS/?. If I was to chisel these out without the chunks going down the drain. I have a couple other huge 4" with clean out stacks coming out of the concrete from the upper levels of the house - the ABS is jammed in and has a compound around the seal.
Since the 1 1/4 inch tailpiece fits perfectly into a 1 1/2 inch pipe and has such a thin wall, is it possible to Fernco this to a regular ABS 1 1/2 inch and go from there with drain/overflow - I know I would be adding to the overall height at which the current tailpiece sits up, but probably only a couple inches?