Cat 3126 mechanical or electronic or both .?????

A friend just phoned and said he was looking for a 3126 mechanical engine . I only got 3126 electronic engines. I always thought that the 3116 was the mechanical Cat engine and when they went electronic engine they called it a 3126 . Is that correct? My friend is looking for a 3126 mechanical Cat engine . Is there such an engine . I would like to know can they interchange . Thanks for any replies .

Cat 3126 mechanical or electronic or both .?????