1970 C10 Rear End ID/Help/Advice

[ShortHaul]

Hey all... bought this ‘70 C10 a few months ago and am going through the truck part by part to get her running and driving properly.

I’m trying to ID the rear end with ultimate goal of swapping the gears for a steeper ratio. I have searched plenty, and found the rear end ID thread, but none of the numbers I’ve found stamped on the rear diff match any of the numbers of the ID’s. I know the truck has been swapped to a 5 lug front and rear, but other than that I have no info about the rear. It’s non-posi, and seems to be a very “Highway friendly” set, so I’m assuming stock 3.07 (3.08?) but I have no way of telling.

The numbers I’ve found stamped on the rear diff are.

“GM 36” on the pass. Side by the fill plug
“A151” with a little sundial looking stamping on the driver’s Side front
“1254333” on the drivers side.

And it’s got 10 bolts to it...

Help!?



And the next thing I need help with is how can I swap to a 3.73 (or so) ratio on the cheap? The motor is cammed, and I just installed a 2400 Torque converter to help it idle in drive, but with these gears it rarely sees the RPM it needs to make power.

My local rear end shop quoted 1200 for non posi gear swap, 1700 for posi. Really hoping there’s a cheaper option out there! Thanks!!

Pics to follow
Untitled by awesome_adawson, on Flickr
Untitled by awesome_adawson, on Flickr
Untitled by awesome_adawson, on Flickr
Untitled by awesome_adawson, on Flickr
Untitled by awesome_adawson, on Flickr

Untitled by awesome_adawson, on Flickr