57 belair diff or 10 bolt ?

I'm doing a v8 swap on my 54 and I'm trying to figure out what to use for a rear end I have a stock rear out of a 57 belair or I have a 10 bolt rear from an 87 S10 which one would be better I don't know the gear ratio in the 57 rear the 10 bolt has 323 gears?

 

The 10 bolt is marginally stronger. I used a 10 bolt because it was a cheaper fix for my broken 57 differential as well as being a little narrower. I had tire rub issues with the old differential. The 3:23 will be a lower gear for running at lower RPM down the highway. The stock differential most likely will be around a 3:55. Not an issue unless you are running a 1 to 1 four speed like I am or plan to race or cruse. All and all the two are a wash in my mind. Use one that is in the best running condition.

 

Would the 10 bolt be a direct bolt in or no? I know the 57 rear is.

 

Obviously gotta mount some perches. IIRC, those s-10 rear ends are something like 54" from flange to flange? May have to move some springs inboard. Stock is right around 59-60 inches(damnit- I should know this spec-it's either 59 1/8" or 60 1/8"), so you might get under there with your tape measure before commiting. Ours is 12 bolt narrowed to 57" flange to flange with the spring pocket kit to comfortably fit 8.5" wide wheel/11"tire, stock wheel well.

 

FYI The '57 is a ten bolt too

 

your s-10 diff is most likely a 7.5 10 bolt. if so I would look for something else.

 

Seening as you want to IMPROVE the rear end
Why not go ahead and install a 9 inch Ford ?? Vastly stronger ... better selection of gear ratios and way better parts availability at even lower prices. The old standby 57 to 59 Ford 9 inch is about 1 inch per side shorter that the original 57 BelAir rear end ... which really makes getting wheels and tires to fit a LOT easier.