hi im new to the site my toy is a 66 impala. im having a motor build with about 370 hrse and got a 700r4 trans. currently i have the stock 10 bolt. has anybody had any problems with these rearends breaking if upgraded to posi and or bigger gears? i probly got 273 or 308s and i know its open. should i just upgrade to the 8.5 10 or 12 bolt? im looking for cheap without welding of course. im probly thinkin 355 or 373 gears. any help, experience or if any one has a 12 bolt it would b much apreciated.