Use the street/strip kit. My transmission used to shift real early until I put in the shift kit. Now I easily get rubber when she shifts between first and second. Don't worry you won't loose any reliability! On the other hand if you don't like how the street/strip kit shifts you can always change to the RV kit (they both come in the same kit).
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1967 Riviera 455 w/switch pitch TH400
ROA#8383
"Life is the intense progression of figuring out too late what should have been apparent at the time."