(89-87.2)/2=+.9mm
137-137.7= -.7mm
.9mm-.7mm=.2mm
using the same piston the ls crank rod setup will sit .2mm higher than the gsr setup. .2mm = .008 inch. A normal gsr setup has a piston to deck of .030". so you would now have .022" deck height which is about the same as a b16a motor.
In other words everything will be fine, good setup just remember to cap off the oil squirters as the cranbk itself will hit the squirter.
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Gracie Barra Clearwater
Gyms in Clearwater, St. Pete and Port Richey
pm me if you are interested in trying a free class at any of the gyms.