Yeah, and I'd print out this post from Stevebfl. He wrote the mother of all postings on properly setting the timing on a 450 SEL. The car in question on this post is also a '73 model.
gas milage (1973) 450sl
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".