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1979 403 ws6 rear end is 2.73s I'm swapping in another 403 for it should be around 350hp. Plan on mating to a semi built 200r4(i have). My buddy is saying I should be looking for an axle with a series 2 carrier and some 3.42s. Does that sound right? Since most are drum brakes would I be able to swap my rear caliper brackets over to make it work?
Thanks!
 

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2.73 is the “beginning” of 3 series carrier which will also accept numerically higher gears up to 3.73 (don’t quote me on that number exactly) so you could replace your ring and pinion rather than replace the entire rear.
As far as whether a 3.42 is appropriate for an overdrive trans, I can’t answer off hand. Someone else may be able to though or look up final drive ratios and/or calculators to assist you.
 

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x2 you already have a series-3 carrier if you have a 2.73 presently, which would also support a 3.42 change. No need to swap the diff, and if so you would also pinch the axles as they are rear disc specific. I also have a 403 with 200-4R and 3.42 rear, but not driveable to report back, but was the setup I thought would best suit what I had in mind for car and driving. Make sure the trans is built for your new torque, not the HP. You'll also need to select new speedo gears that also match your tyre diameter, some gears are getting very hard to source for these. If you still have your original 403 Q-jet, you are winning as these did not require any mods for the new TV cable like nearly every other, just the new bracket for that holds both cables to the base.
 
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