You need to move the crankshaft pulley and flywheel over so the pully can line up approx with ctr line of the governor and then th eflywheel enough to clear the belt. Outrigger bearing support will also have to move. The crankshaft will have enough length for this.

You might get away with the pulley up against the eccentric but check the belt clears the eccentric rod particularly near the governor. This does risk the belt slipping as it is at more of an angle. Flywheel will have to come over so it’s hub will have to touch the outrigger bearing and if lucky you may be able to turn some material off that side of the hub, just make sure it clears the bearing support. Otherwise you are going to muck up your paving to move the bearing support

My belt is 235mm end to end

Excuse the dust, Flywheel could be a bit closer than I have it

The reason for the “original design mess” is that the drawings for the basic beam engine give a distance for the outrigger bearing from engine ctr line. This gives minimal overhangs.

Adding the governor as an extra needs the outrigger and flywheel moving. It is too long ago for me to remember if a distance is given on the governor drawings or not, But if added after all the base has been made then you are a bit stuck.

It is the same for several Stuarts if you add governors, pumps, reversing sets then existing parts need to be altered adjusted or replaced