ive got the split port SOHC it has a max tourque of 3,750 where the Zetecs have it at 4,500
thus the SPIs have a deeper geard set up.
final is 3.61 or 3.85?
O\D is about 25%
its a IB5 trans thats with the spi, but i don't think it would bolt up to a Zetec
keep on the look out for a under drive pulley, the common one is for the crank. but there's also a alt and water pump one.
new there rather spend-y so keep on the look out for used ones.
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1 86 T\D trooper with rare GEN 3 rods
TRANS FIXED 
NOW DD
1 86 4WD 5sp pup is 2.3L gas, but plan on 2.2L diesel repower
1 91 trop, long term plan is a group buy of imported Isuzu 4JB1-T 2.8L I-4 engines, hoping to get price down to 2K not 3K plus
1993 sidekick my MPG toy, epa rating 26.
i get 29/31 with stock drive train.