Quote:

Is the general rule of thumb about cast crank having the thicker balancer gone??



It's a general rule that never applied to 318's or 273's.

As mentioned, 318s are neutral ballanced with either cast or forged crank.

Here are some part numbers

year cid material cast#/forge#

64-67 273 forged 2128278, 2128869, 2205700

68-69 273 cast 2658268, 2658393

67-73 318 cast 2658278, 2658393

74-86 318 cast 2658278, 2658393, 3462387
2658391

68-72 340 forged 2532457, 2843868

73 340 cast 3462387

71-86 360 cast 3418640, 3418641, 3418642