a904 to 727 swap help!

I blew up my a 904 automatic in 74 duster and am looking for a replacement 727 or 904. Is the 727 a bolt in? What are the different tailshaft lengths? Does anyone know a supplier where I can purchase either a 727 or 904 to replace the one in my duster. I'm looking for a fairly sturdy transmission that will allow to me to build a gnarly motor then my current stock 360. Thanks for the help.