Take all the windows out, glass is heavy.
That means you could also remove the window winder mechanisms and motors, which also weigh a lot .. then all the associated wiring, burn the plastic off and sell the copper wire, might get some money for it that way too ..
Lots of odd wires and pipes in the engine bay, I'm sure some of them could be junked .. just wave a recip saw about, and lob the bits away, you'll be OK ..
Diesel is also quite heavy, so make sure you bubble helium gas through it, and only have 3 litres of diesel in at a time.
I also find most oils, like diff oil and gearbox oil can be junked, and you could even use this in the diesel tank .. saves buying diesel, so a saving there too ..
Don't bother with a tax disc holder, some of them are excessively over weight, just lick the front of the tax disc, it'll stick!
Bonnet is also heavy, remove all the soundproofing, then the bonnet, they weight loads. Get some thin hardboard to cover it and a light spray of paint so it blends in and for waterproofing, it's a well known mod amongst 1pw's.
Get the smallest shocks, springs and tyres you can find, slam it to the ground, less weight ..
Lower the roof, cut the pillars down, small bit of welding, big returns on weight saving.
Anything that's bolted on, check the bolts and remove every second one, for instance the sump I believe has about fifteen bolts!! FIFTEEN, ffs, remove seven of 'em, halved the wight right there .. I'm sure the transfer and gearbox covers can be done similarly, and the head, rocker box, timing case .. just imagine the weight savings.
Actually, just buy a Fiat Panda .. they're only about a quarter the weight already ..