Wondering if the advance curve for the preceding M116 3.5 is "better" than was used on the M117 which had to be designed to meet more stringent US smog regs that went into effect in 1972. If so, can the M116 curve be achieved merely by switching advance curve springs?

__________________
Berfinroy in CT
Present vehicles:
1973 300 SEL 4.5
1959 Rolls Royce Silver Cloud I
1973 Citroen DS23 EI five speed
Past vehicles;
1959 Thunderbird convertible/430
1958 Bentley S 1
1976 ex-Max Hoffman 6.9
1970 300SEL 2.8
1958 Jaguar MK IX
1961 Jaguar MK IX
1963 Jaguar E-type factory special roadster
1948 Plymouth woody
1955 Morgan plus 4
1966 Shelby GT350H Mustang