The only true 'lightweight' bodyshells from early production were the 'PZR' bodies of the PS30-SB Fairlady Z432-R models. Their rear quarter panels, roof skins, front wings and scuttle panels were made from one gauge thinner steel than other models, all other bolt-on panels were FRP and all glazing apart from front screen was Polycarbonate. No sound-deadening, and little in the way of interior trim.
Most of the other 1969 through 1972 bare 'shells were about the same weight as eachother, give a Kg here or there. It was what was attached to them that made the difference.
Factory quoted weight for 1972 production UK model 'HS30' ( 'Kerb Weight' = with oil, water and half tank of fuel ) = 1,038kg.
Factory quoted weights for Japanese market models, all quoted for standard trans ( 4-speeds for 'S' models, and 5-speeds for all others ), with 'Standard' equipment levels and 'Dry' ( no oil, water, fuel ):
S30-S Fairlady Z = 975kg
S30 Fairlady Z-L = 995kg
PS30 Fairlady Z432 = 1040kg
HS30-S Fairlady 240Z = 985kg
HS30 Fairlady 240Z-L = 1005kg
HS30-H Fairlady 240ZG = 1010kg
*Accessories / Options will affect weight.