This wouldn't be a subject for discussion if Mr T had the foresight to galvanise the chassis in the first place.
There woudn't be any competition either because the other makes would have no customers once the market realised a LC bought in your 30's if maintained meticulously could see you out, even in Britain where we have a fetish for dumping millions of tons of aggressive salt daily on the roads every winter, when in practice its needed only a handful of winter days south of the border.
For best underbody washing results i usually wash under several times during the winter any to stop salt building up, then last week after driving through heavy rain i drove through a local ford several times and once back home finshed the job off with my pressure washer, to which i have an L shaped lance fitting that has a particularly wide spray pattern , as said above you don't want silly high pressures you want a high flow rate and plenty of water.
Just waiting now for the warmer weather so can get underneath and do this years proofing.
Altering my method a little this year, going to be a combination of grease over accessible surfaces and ACF50 spraying in the more awkward spots (would try chain lube but got 8 litres of ACF to use up), plus its time inside the chassis and sills etc were redone with the Bilt Hamber cavity probes.
Just out of interest, there is (assuming still in business) a place near Doncatser i think that does proofing, supposed to be pretty good at prep work and somewhat more reasonably priced than what we're seeing so far, i don't have details so its a case of look em up.
Dave_S, your bodyshop sounds like the proper full job, can i ask how much that's going to cost.
It would be interesting to see under my 57 plate Hilux again and compare with similar vehicles not treated when new, it was intended as a long termer meticulously overserviced and babied but found we had no need of it after 3.5 years and sold it on (depreciation was excellent), looking back should have kept it, a trader up Harrogate way bought it, whoever bought that motor from him got a really good truck, have watched the MOT history since not a mention of corrosion anywhere, couple of years ago advisory front headlight and/or lenses, whether sun or other damage is unknown.