Checkout this link down below your post - A well tuned and intercooled setup - approx 420kw at the crank (320kw at the rears) is just the start from Justens Celica V8 - an awesome beast with more to come.
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JustenGT8 JustenGT8 is offline
White Belt...
Helper spring is ok, I would go with pulling it apart and fitting a lighter spring. Other options, shorten the arm or change the location point to the push/pull rod, add a lever to halve the load.
diff ratio
2.92 seems a low diff ratio Justen, factory is 3.9? How does it feel off the line and in gearchanges - not too wide? What revs does it cruise on in 5th gear?