11R143970 This is how to ID the engine to the car, if the division (1), Year(1), Assembly plant(R) and the last 6 digits match the car VIN then its the original engine.
1=Chevrolet Division
1=1971
R=Arlington assembly
143970=Car sequence number, last 6 digits.
TO204CJD
T=Tonawanda Engine Plant
02=Feb
04=day
CJD=1971 Chevelle 350Cid/270hp w/4BC rpo L48
Vin number 136371R143870
1=Chevrolet Division
3637=Malibu Sport Coupe
1=1971
R=Arlington Tx assembly
143870=sequence number and would also appear on the engine, the 11R143970 I bet is really 11R43890? Look again, if it is this is the original matching numbers engine!
As you can see nothing here will tell you any options and the SS was an option not a model. You will need paperwork to authenticate a SS, sure you can look for all the obvious SS equipment but even that can be retrofitted by knowledgeable persons. There is info on this site to help with that and I won't get into it. All 1971 SS had 12 bolts with the exception of the the L65 350/2bc SS with a manual tranny (not a 4-speed). This engine you have is a L48 and should have a 12 bolt. Posi was never standard, it was always an extra cost option. If no 12 bolt is present I would start to become suspicous otherwise chances are good its a SS if everthing else is there.
[This message has been edited by elcamino (edited 07-18-99).]