Vintage Cars: 1976 mercedes 560sl, limited slip differential, good liar

Question
i came across an old man who has a 1976 560sl, i thought they started in 86'. it had a 5.6 in it and badges on the door post said 76 as well as on the core support. the 560SL emblem on the back is original too, no evedence of it being tampered with, the paint is original and peeling away normally. is this possible or is it just a 450sl "converted" into a 560? the old guy who had it said he bought it brand new and doesnt know of anyone who took it and changed the badges or engine without him knowing and that its practically how he bought it new, just aged. any tell tale signs i can tell the body of a 450 from a 560? he dosnt have any of the paper work but on the registration it even says 1976 mercedes 560SL! how is this possible?... or is he just a really good liar? haha. thanks

Answer
impossible quite honestly .  What do the build plates list as chassis number and engine #
560 SL  - Chassis: 107.048 , engine V-8 (117.967)
The 560's all had limited slip differential , front air dam and leather ,anti theft alarm was standard, will have ABS and I believe a driver side air bag, hood would be  aluminum
Let me know what you find!