Not that I know much ( I Know nothing - your honour), but I once saw a cut down range rover chassis where, instead of cutting straight down, the guy cut the chassis in a dove tail, sort of, so that the weld was much longer, and thus stronger.
God, what a rubbish way of describing it.
Right. Imagine that the cuts on the top and the bottom of the chassis rail were, say, 4 inches behind the cuts in the sides, with the joining cut along the corner. Does that make sense? Anyway it was neat.
Anyway please don't cut up the series, scrap the body work of the disco (you'd get paid for that!) and buy new panels from one of the parts suppliers and make up your own bulkhead and front panel.
MUCH better, as you can do what you like for engines and radiators etc.
G.