I spoke with James O'Neal regarding the feasibility of doing the 60K Cline mod to the 60B. James said Steve Helms looked into it but found it wasn't practical to do so with the 60B.
Go with the 60K. I don't think you need a carb mod on the 60K with a Cline or Iron Bay and your OS70. Just run the Cline and your stock 60K. I'd bet it runs fine.
The carb mod probably wouldn't help you much with a stock 70 head. If you had a dual plug head you may benefit from it.
I believe the Cline and carb mod. compliments the Dual Glow Viperhead by allowing more fuel at top end to enter the motor as the dual head can burn more fuel per stroke.
That's why the Cline with the modified 60K generates so much power when used with a Viperhead and Cool Power 30%.
Predator Gasser SE/231 X 2