Can I change my B.O.P rearend from my 2.78 to 3.55's? i've been told that you have to get the larger carrier to put 3.36 and lower in. However, i've seen some people on this forum say they've done what I'm thinking about. So, what are the facts? Oh, ya, the rearend is in my 1969 firebird, if that changes anything. I was also thinking about just finding a 12-bolt out of a camaro or a nova and just using this. What would all of you recomend?

Can I change my B.O.P rearend from my 2.78 to 3.55's? i've been told that you have to get the larger carrier to put 3.36 and lower in. However, i've seen some people on this forum say they've done what I'm thinking about. So, what are the facts? Oh, ya, the rearend is in my 1969 firebird, if that changes anything. I was also thinking about just finding a 12-bolt out of a camaro or a nova and just using this. What would all of you recomend?

Do you mean a gear change? If so, then no, you cannot go from 2.78 to 3.55 using the same carrier and housing.

The break off point for the different carrier and housing housing was 3.36 - Well, maybe the housing is OK, but the carrier will definately have to be changed

You will have to replace the carrier to use 3.55 gears; your factory rear end housing can be retained.

Any recommendations on companies to go with? Is the Eaton Unit a good choice?

I'm in the same process. I almost bought a 3.23 posi that ends today on ebay but everyone thinks I should go with the 3.55. Between the posi unit the gears and the kit it's about $700 at Murrays Speed. Brands are Auburn and Richmond Gears. I am going to pay $250 for the labor, I might screw it up.
Hope this helps,
JG