The biggest servo is the R servo. All the other letters are smaller. All 428CJ / SCJ applications used the R servo. The 1967 - 68 Shelby GT500 used the H servo.
I do not have any information on an E servo. I would need to look at the case to see the part number on the case to possibly determine what it might be for. It's not a performance application.
Here they are from weakest to strongest:
N 1.93 2.92 Molded piston
S 2.00 2.86 Molded piston
G 2.04 3.02 O-rings
J 2.07 2.69 O-rings
L 2.07 2.98 Molded piston
D 2.08 2.98 O-rings
P 2.10 2.86 Molded Piston
H 2.34 3.02 O-rings
R 2.48 3.50 O-rings
The first year for the C6 was 1966. All 1968 and newer C6 transmissions have a VIN stamped on top of the case which makes identification super easy. You need to tell us the casting number if there is not a VIN.
My other c 6 has a d. What is the difference between a d or e and what would have been the application