i found my chassis numbers stamped into the chassis rails in 3 places all matching so if your going for a full rebuild you might get lucky and find one of them
to find the numbers theres 3 main reported places
1 on the drivers side front chassis leg about 4" back from the verry front spring hanger
2 on the passengers front chassis leg on the inner side about 2" up and 3" back from the spring bush going through the chassis rail
3 on top of the passengers side chassis rail roughly 27" from the rear crossmember ( you will have to remove the rear tub to see this )
as with anything this old the numbers will be verry faint and near impossible to see due to corrosion wich is the problem i had in the end i resorted to google for ideas and information on a forrensic level to make these numbers more visible so ill save you the bother and just explain
first scrape all crap paint and underseal from the immediate and surrounding area and look closely for anything that could be part of a letter or a number in amongst the pits and rust
once you have spotted a likely looking mark first rub it lightly using a little warm water and a brillo pad if it turns out to be a number carry on till you find all the digits if theyre still not clearley legible then resort to pouring a little t-cut on the numbers and use 800 grit wet and dry sand paper verry lightly over the area and you will notice as the polish starts to turn black it stays in the indentations while any on the flat surface will wipe away pretty much clean and bright metal ( in effect the digits will show black / grey on a silver surface )
note if your gonna try and get the reg from the dvla from this chassis number once you have cleaned it paint it with either clear coat laquer or if you havent got any knocking about coat it with superglue or clear nail varnish to protect it from the elements
if your repainting the entire chassis mask the area where the number is stamped and paint round it as this is a key must do thing if the dvla request the vehicle goes for an IVA test due to it not being on their database this proves you have just found the number and are leaving it in a honest condition clearley legible for the inspectorate to see
also take pictures of the process of finding and cleaning these numbers and save them as evidence you have not tampered with them or stamped them yourself ( this was the triggering factor that made the dvla question when and wher i purchased the vehicle )
hope this helps
ps dont put pics of the chassis number on any public domain website not here not facebook ****ter or anywhere keep the number to yourself and the dvla as you never know whose reading what you post anywhere