1.75:1 is often refered to as the perfect ratio. From what I've read, they both have a bad ratio, (the same one)!
"B18A-B; B20B-Z:
Rod length: 137mm
Stroke: 89mm
R/S: 1.54:1
Displacement: 1834.47 cc"
Taken from:
http://pub72.ezboard.com/funleadedra...icID=775.topic
This guy posted a lot of good info.