1996 4.0 serpentine belt question. What am I missing?

As part of the work on Otto (head gaskets, etc), I noticed during disassembly that the serpentine belt looks pretty old and worn. So plan to replace it. However trying to get the old belt off today seems impossible. The gap between the top of the crank pulley and the bottom of the water pump pulley seems to be about half the depth of the worn belt, so it won't fit through.
Let alone trying to get a new belt through the same gap.
Water pump was changed not that long ago by previous owner - do they come with different size pulleys? Is that where the problem could be?
I haven't been able to free the viscous coupling nut - seems solid despite big spanner. penetrating oil, bracing the waterpump pulley, skinning elbows, etc.
Is it possible to move the water pump pulley away from the engine a bit by loosening / removing the pulley bolts without the viscous fan nut undone, or does the nut keep it tight regardless?
Then, from a lot of the posts on here is the fun of finding a new same code drive belt doesn't want to fit round everything it is supposed to....

I expect the front of your engine is similar to my 3.9 so no special tool just a large adjustable on the large viscous coupling nut give the top of the spanner a large wack or two to crack to hold and the coupling with the fan will spin off anti-clockwise.
The coupling releases in the opposite direction to that it spins when the engine is running.
A genuine parts book will tell u the exact pt no u require for a genuine serp belt for your engine, assuming its still as it left the factory.

But I expect u know that by know.

Cheers. Managed to wangle the belt out between the pulleys with advice from @kermit_rr about how he did his. So I should be able to get the new one on that way too in due course.

Viscous appears to have been gorilla'd on - tried everything in my fool box and it isn't playing, so now looking at making something to bolt onto the pully to try to lock it enough to get the viscous off. At least then I can get to the crank pulley to check my rocker shaft clearances when the skimmed heads come back.

Scotiawhiskers said:

Cheers. Managed to wangle the belt out between the pulleys with advice from @kermit_rr about how he did his. So I should be able to get the new one on that way too in due course.

Viscous appears to have been gorilla'd on - tried everything in my fool box and it isn't playing, so now looking at making something to bolt onto the pully to try to lock it enough to get the viscous off. At least then I can get to the crank pulley to check my rocker shaft clearances when the skimmed heads come back.

Click to expand...

Assume you mean taking the viscous off the water pump... I did mine with mole grips and a long screwdriver, if you're careful you can stop the pump turning while the grips undo... Will be obvious when you look down

In the end, the only way I could get the viscous coupling off mine was a new water pump! Couldn’t find any way to hold it enough to get enough torque to budge it. I am sure I could have got there in the end, but found enough okay in the WP bearings that I decided to replace it anyway