Hi, I own a 1965 Oldsmobile 98 Holiday Sport here in the UK.
I need 2 new key blanks, my original key is stamped with a "C".

Thanks
Spotswood4444

 

which style head of key, round or stop sign looking?

 

That's not an original key. The original key blanks for all 1935-1966 GM cars were the B10 and B11 blanks. The lettered key blanks were first used in the 1967 model year (and those would have been "A" for the ignition and doors and "B" for the trunk and glovebox). The "C" blanks were first used on the 1968 cars and again in 1972 and 1976. Your lock sets have been replaced with either newer ones or aftermarket sets.

 

Rather than resurrecting an old thread that is only partly relevant, here's your own thread on this topic.