Are you sure the starter is re-energising or is it just still running? Aren't some glow plug relays timed, as in they stay on for certain amount of time even if engine is running.?

https://parts.jaguarlandroverclassic.com/nrc7009-bar-underside-protection.html

It is an actual Land Rover part which isn't cheap for what it is. My son has one on his Ninety, I quite like the look of them but in reality are probably pretty useless.

Really, what about the rust inside the chassis, you can't galvanise rust. It will carry on rusting from the inside out.

Isolate the spotlight wiring for now and concentrate on finding your headlight problem first.

They're just yellow Britpart ones - nothing special. Standard height. The last lot did me for 12 years so they're clearly not too bad.

Which springs did you buy?

I've had a go at the rear suspension bushes and ball joint. I last did them in 2013, so they've been good for 12 years. I did a whole thread on this in the autumn of 2013 so I shan't repeat it here. Plus I forgot to take very many pictures...

Why don't you draw a picture of exactly what you have wired to where for better help? It's taken 2 pages for you to tell use that you have fitted a fuse and relay.

Sorry, I meant the company in the link might have one.

Leave it in some very hot water for a few minutes

https://injectionpumps.co.uk/product-category/spare-parts/bosch-spare-parts/ve-spares/ Might have one.

How can you galvanise a rusty chassis? Can you acid dip it first to remove all the rust on the inside?

They are as tight as hell, warm it up first.

I had to bleed my son Ninety with the wheels off the ground..

Maybe he has fitted some relays?

Welcome to Landyzone.

Interesting, mine pass and so do my son's on both his Ninety and D2.

Don't presume the new battery is any good, I had a Bosch one which failed within a week. If you have a flat battery, jump it and leave it running with the charge light on it will still be flat, well flatter, than when you started it.

Joints on the ends of the propshafts.

Exactly

All of which have potential to go wrong, unfortunately. It's a job I would try and avoid if possible, ok you're not going to do it for the sake of it but you know what I mean.

Bear in mind you might want a relay or two and a fuse before you burn your truck to the ground.

It's an easy job if the studs don't snap or damage the threads in the head.

Agree there should be clamps to attach to the gutters, no drilling involved.

Rear suspension bushes and A-frame bushes. Chassis damage to A-frame cross member or even trailing arm chassis mounts.

Mismatched wheels and tyres?

I would suggest you get underneath and physically check the propshafts. Even better take them off and check them, do you ever grease them? Take one off and drive it in diff lock see if the noise is still there.

There is a little metal ring on the hose, it should have the part number stamped on it.

Because the 1986 Landrover Ninety's had glass fuses not those moden bladed ones you have.