What kind of power can a stock '54 rear end hold before going poof? car has no engine or tranny, so whatever i put in, i dont want shreading the parts that are there. and if it will, then perhaps ill just upgrade before it has a chance to go poof.

 

About 108 HP...

Sorry...I couldn't resist. It really depends on how you drive. If you are doing 5,000 neutral slams every time, 108 is the magic number but if you baby it and leave soft every time, it will handle 500. It's all on you.

But, that being said, I just bought a Ford 9' with 31 spline axles to put in my '62....

 

For all practical purposes, the 53-55 Corvette rearend is the same as the 49-54 pass car rearend. The pass cars had either a 216 or a 235 6cyl engine with a 1bl carb. Not a whole lot of power there! The MAJOR difference between the pass car rears and the 53-55 Vette rears was the driveshaft. The 49-54 cars had a closed driveshaft (torque tube), while the Vette rear center section got a conventional U-joint/open driveshaft arrangement. Otherwise, the internal guts were the same between them.
After I wore out the first engine (216/3sp) in my 51 Chevy, I replaced it with a 261 truck engine and the Corvette 3 carb setup and promptly broke an axle with it!
The 55 Vettes got a V8 (265) with a 4bl carb and PG tranny (except for about 75 that got a 3sp) in front of this same rearend. With a 265/4bl engine in front of this style rear, they seem to have held up fairly well. But I sure wouldn't trust one of those rears to last for long behind a healthy, larger displacement SB, such as a healthy 350.
A simple, bolt-in swap for a stronger rear would be a 56-62 axle housing with a posi center section. Positraction was available in 57-62 Vettes and that exact same center section with posi was available up through 64 in full size pass cars.
I have this type rear in my 56 behind a fuel injected SB400 and Muncie and it's never given me a moments grief.

 

i guess thats good to know. though kinda sucks too.... i wasnt exactly planning on doing a rear swap, but for safest reasons, its probably better i do it now. it will be the "wifes" car, and if i put anything evendecently fast in it, sounds like she'll blow out the rear.
anyone wanna buy a 54 rear :P (just kidding, for now it will not be sold! unless you wanna trade me for a front end )

 

The weak is part on a 53 to 55 is the rear gears .it blow you cant find or get any parts to fix it , your only choice is to go to a 56 to 62 Corvette or car but you need to move the spring pads .