Running hot & cold

I'm kit up to fit a pressure release thermostat to the front of my f; I'm very fond of my head gasket & any potentially ruse to lengthen its life gets a thumbs up from me. The original thermostat has to come out & that means a bit of work around the thermostat housing, however looking in the workshop manual cooling section for the VVC, changing the thermostat seems to be nothing other than a quick “flick of the wrist”. The MPi section on the other hand has half the arse end on the car on the bench, are the engins so different? As yet I've not been in a position to look from the top or the bottom to see how easy/difficult it might be. Any comments on both halves of the job please.

The difference is the inlet manifold. The vvc has a two part alloy one. Easy to take apart.
The mpi has a one piece plastic jobbie that's a pig to get off.
The thermostat housing is hidden by the manifold.