Apart from the standard LSD gearbox, which some RST's came with, what others will fit? without any modifications.. just a fit and go?

I need a new gearbox, and i am going for a different setup soon but still want to use the car to travel to shows and back. i need a gearbox at a good price, i dont wanna fork out 100s for a LSD as atm i cant afford it,

So what gearbox's fit? without any messing around. and more money being spent. as i need the cash for my new one im having started in sept.

1.6 XR3I box? i here you can get them cheap. but how cheap?