4WD Gearbox Conversion

[Fat_Panda]

Is it easier to convert a RWD gearbox to 4WD by placing a transfer box between the gearbox and propshaft, rather than swap in a whole new gearbox? This is for use in a car, and I ask because I a transfer box out of something like a land rover goes for £50 whereas the gearbox out of a 4WD car like a Ford Cosworth costs circa £350. It seems more practical to use just the transfer box, rather than swapping in a completley different gearbox and having to get a custom bellhousing made...