Which transmission should i use?

I have a 727 in my 64 Signet and did not do any hammering or cutting what so ever, its also a 1962 BB transmission with push button shifter. Now I don't know if there is a difference in regards to the space where regular shifting thingies are but it has plenty space on the shifter side. All what was changed going from a 904 to the 727 the driveshaft and the mount which I fabricated from the 904. I don't think things have changed that much in 25 years outside or the 518 length if you're going to use one.