I agree with Vince, but want to say it is all in what you want out of the car. If you are looking for a cruiser and mileage, then go with the 3:36 and see what happens and if they don't work then go to the 3:55.
If you are looking for acceleration and are not concerned with mileage then go with the 3:90 or 4:10. As stated it will keep the engine happy and give you some good get up and go.
I have 3:42 with a 5sp, not on an LS, and it was a good balance for me. Gave me a little pep and also gave me good mileage.
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'89 IROC-Z Turbo 3.8 5SPD
LS1 Brakes|Wilwood Prop Valve|LS1 Master Cylinder|Aluminum Driveshaft|LS1 3.42 Rearend|Adj PHB|Adj LCA|LCARB|Koni Struts|Koni Shocks|Adj Caster/Camber Plates|STB|10 Spoke SS Wheels|PHB Relo Kit|Adj TA|SFC|ARAP Based Prom|B&M Short Shifter|Underdrive Pullies|SMOG!|AIR!|Rag Joint!|Magnaflow|Ported Plenum|Misc Stuff
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