C20 8 Lug Dana to 12 bolt swap

[Big Kev-O]

I have a 68 GMC C20 and plan on converting to short bed with trailing arms. Truck will be used as a weekend warrior for spirited driving. I can either install all this with the 8 lugs and buy some Detroit Steel wheels which are expensive or put all 6 lug gear which open up all sorts of wheel options. I have the opportunity to purchase a 12 bolt from a 72 K10 with locker and new gears for $500. My Current SBC makes 350hp and I will probably never exceed 600hp since that is all my FiTech is capable of.

What would you do ? I’m looking for the most affordable approach.

Is that 72 K10 12 bolt durable? Is $500 fair?

Is the diameter of the Dana tubes the same as the 12 bolt? In other work will a Dana bolt up to trailing arms if I weld some perches on it?

Thanks for the advice!
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[Captainfab]

A truck 12 bolt is a lot tougher than a lot of people give it credit for. With your 350hp, it is a piece of cake. if you start getting up towards 500hp, I would consider aftermarket axles, if it doesn't have them al;ready, and welding the axle tubes to the center section. A good 12 bolt with a locker and gears that you can use for $500 is a decent deal.

The Dana 60 is a good tough differential, but it would likely need a posi/locker for what you want. It can be changed from 8 lug to 5 or 6 lug but that is $$$$. If you can find some wheels you like in 6 lug, I would go that direction. Front disc brakes in 6 lug is easy.

I make trailing arm mounts in for both the Dana 60 and the 12 bolt. The axle tube diameters are not the same.

[Big Kev-O]

Thanks for the knowledge Captain! I have learned a lot from your posts since I joined this site years ago. I will go with the 12 bolt since I don’t see myself going over 500hp any time soon.
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[SmirchIs#1]

Originally Posted by Big Kev-O

Thanks for the knowledge Captain! I have learned a lot from your posts since I joined this site years ago. I will go with the 12 bolt since I don’t see myself going over 500hp any time soon.
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I agree with captainfab 100%.However you stated the rear you're buying has a locker,which is great if it's a true locker.If it is the original Eaton posi unit,they are prone to cracking in the lower left corner of the openings that you load the gears & clutches into the posi case.I have several cracked ones on the shelf that I have kept just for parts over 40 years of doing rearends.Eaton has rectified this prob. on the new units buy adding much needed material in the critical areas.The newer unit will handle 500+ HP

[Big Kev-O]

Originally Posted by SmirchIs#1

I agree with captainfab 100%.However you stated the rear you're buying has a locker,which is great if it's a true locker.If it is the original Eaton posi unit,they are prone to cracking in the lower left corner of the openings that you load the gears & clutches into the posi case.I have several cracked ones on the shelf that I have kept just for parts over 40 years of doing rearends.Eaton has rectified this prob. on the new units buy adding much needed material in the critical areas.The newer unit will handle 500+ HP

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[Big Kev-O]

Seller says it is a 3 stage locker so I don’t think it’s factory stock.
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[SmirchIs#1]

Originally Posted by Big Kev-O

Seller says it is a 3 stage locker so I don’t think it’s factory stock.
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There are many different names for posi units.A true Detroit locker is exspensive ($700-800) & superior to the Eaton stock clutch type unit,even the new version.Stage III could simply mean Series III.A stock truck 12 bolt with ratio of 2:56 or 2:78 is a series II, 3:07 & 3:40 is a series III,3:73 thru 4:56 is a series IV.You need to get the facts.While the 12 bolt you speak of sounds like a heck of a deal,depending on who built it,it may not be for you if you raise your power level above the 350-400 HP level.The cracked posi units I speak of are out of STOCK application trucks.

[GASoline71]

A K10 12 bolt will have leaf spring perches welded to it. If you're going to switch over to trailing arms you'll have to cut off those perches and weld on new ones for trailing arms.

Gary