John I cannot answer your question directly but my DRB with a LS1/G50 weighs in at 1120kg you my get an idea if some other DRB owners with Winsor /G50 combinations can supply their weights.
A G50/52 is 75 kg or 165 lbs. That is dry without TOB, or slave cyl and mechanism or starter. A non turbo box may be slightly lighter but nowhere as low as 50kg IMHO. A 4 speed 930 with smaller and fewer gears and slightly larger R&P weighs in at 57kg/125lbs.