Why would you put a 4 speed auto up to a 18R ?
you would be better of with the 21R and 4 speed auto
staight out of a RA60 !
fit a Weber 32/36 DGAV , 22R cam & headders .
give it a port job and the motor will rev to 6500 no probs.
And it will run 96 ron pump fuel unleaded . no cat .