Kartman24

I am doing a gearbox swap on my car as the current one with the round flange is well past it`s best, it was an all syncro box (not any more!). I have a Herald GB suffix box which i would like to fit as it is supposedly a NOS box i have had for a number of years but it has the square flange on the rear of it, are these rear flanges interchangeable? I know another option would be to change the flange on my propshaft but i gather there are two different sized yokes and i don`t have a square flange here to fit to the prop. I realise the box going in is a non syncro on 1st but i am not really bothered about that.

I have an all syncro 3 rail box on my 1300 engine but the gearbox has now had it, i have found a new old stock box but it has the square type rear flange, my old box has the later round one. Are these flanges interchangeable between the gearboxes?