Replacing the chassis on my 1986 90 early next year, Richards chassis ordered with a delivery date of March which will leave me a couple of weeks to prep the chassis and then I will SORN the vehicle 1st April to really get stuck in.
As already stated, the shopping list will be extensive (unless you have kept on top of things over the years) so whatever you think you will need, you are likely to need much more as you get it apart.
The list from DAG019 is about right.
I can thoroughly recommend the use of SS fixings (suitably lubricated of course), I first used them on mine 19-years ago and whenever I have to remove items they come apart with ease (haven't suffered a seized screw / nut or bolt since).
I had my rear tub off this summer to get it stripped & painted ready for the re-chassis (I just want to remove the tub as a single lump next year rather than stripping it down and sending it off to be re-painted then). Everything came apart fine but I did have to replace things like the metal fuel filler tube which was looking distinctly worse for wear. Likewise I will be replacing the fuel tank & pipes, the tank still looks sound but it is at least 20-years old (as long as I have owned the vehicle) and even though it has always been Waxoyled it can't last for ever. I also fitted galvanised steel doors, had them painted and built them up so next year I just move them across as built up units with no worry of there being any corrosion present. A bonus is that I can align the bulkhead etc to suit the new doors and not have the hassle of re-aligning at a later date. If you suspect that your bulkhead may be anything less than sound then you are looking at stripping it whereas it is nice if you can swop it fully built up, if it does need repairs then make sure they are done with it bolted to the chassis to make sure it fits! Likewise you may find corrosion to the alloy panels and as already stated, you may need some YRM repair panels.
I wouldn't worry too much about a definitive shopping list at this stage, as you start to strip it down you will see what needs to be replaced and most items are available in a couple of days but I agree that you should consider doing whatever is required while you have all that lovely access and it is a good way of pricing the job up so you aren't in for too much of a shock when the time comes!