Gear ratios vs tire size
 

Ok so I bought a running donor truck so I can switch my 92 over to a 5 speed, it has the ls rearend which I was also going to use. upon cleaning the tags I see that it is the 4:10 version and my truck has the 3:54 so I would have to use both front and rear. My question I guess is what tire size would I have to use to make the 4:10 work the same as the 3:54?

IIRC going from a stock size tire to a 37 is close to going from 3.54s to 4.10s.
So what I am trying to say is a truck with 4.10 and 37 inch tires will turn similar revs going down the road to a stock tired truck with 3.54s.

Thanks Oliver that's kinda what I was afraid of...I really don't want to have to put a lift kit in it just to run 37s:badidea:

Pick a tire size you can be happy with then change the ratio adapter to correct the speedometer reading. Your engine will run a little faster, but it will also transfer some more power to the ground.

I run 4.10s and 37 on my white crew cab. I installed a 3.5 geared unit in my NP-205 from another truck and the speedo is now very close.

I did the same 20 years ago with my '72 Power Wagon with 38x15.5 Super Swampers on it.