will my 8 1/4 rear hold?

An 8-1/4 will hold up fairly well to a stock 400, but are you sure it's an 8-1/4? I didn't think there were any big bolt 13" wheels or small bolt 8-1/4's.

no, the fronts are 13's and the rear is 14. isnt the pattern the same? 5 on 4?

The 8 1\4" was used in some trucks and vans so it should be fine behind the 400>

If the rears are small bolt (5x4") the rear end is most likely a 7-1/4 and that won't hold up behind a mild small block.

yeah, it is a 7 1/4, but they did use that rear end behind the 273, so i dont know. well see how long it lasts.

Yes, they used it behind the 273, but it was a time bomb in those cars, especially with a four speed (don't ask me how I know).

all I need is one good power brake!

a ways back I had a 64 val. station wagon and the 7 1/4 just up and left just tooling down the high way. Yea they used the 7 1/4 behind the 273 but when they opted for the comando 273 it went to a 8 3/4. The 8 1/4 will hold up to alot even with welded gears but the 7 1/4 well lets put it this way take the axels out and put a strip down them and then weld up the gears and pull them out a week later and put out the candy cane. what I did was go the junk yard and pulled out a 8 1/4 from a aspen station wagon its held up for me. even with the welded gears.

The early 273 four barrel cars had 7-1/4 rears, even with a four speed. Mine sheared an axle off coasting to a stop...........

I had a 66 cuda 273 power pack with the auto trans and a 3.23 sure grip 7 1/4. Swapped the engine and rear into my 68 cuda street car when I found a 340 and 8 3/4 for the 66 race car. Still going strong when I sold it.