Is it possible? how much trouble will it be?
 

So I have a 455 sitting in my garage that I am looking at putting into a 77 omega that currently has a 307. From the research I have done, it seems as though everything will swap without major problems and it will mount without any fabrication. If I am wrong about the fitment of the 455 into the omega, please let me know. The question I have is what I need to do about the transmission and suspension. Obviously the engine is heavier and I will want to beef up my suspension, but can I get away with just springs or will I need more? I have the transmission for the 455 (not sure specifically what it is as I am new to Oldsmobile stuff) but it needs rebuilt before I can use it, so could I use the transmission currently behind the 307 for the time being or will I just wipe it out as soon as I start driving?

Thanks, Brian

It SHOULD drop right in, but I don't have any personal experience with the X body so I'm unsure about clearance with the heater box and steering column. Those would be the two major areas of contention you would have to deal with.
Make sure to use the same motor mounts that came off of the 307.
As far as the trans in the car goes I have no clue if it will hold up at all. you haven't told us what it is or what condition it's in.

I believe the transmission is a TH350 in good shape, as good as a stock build is.

Well they put TH400s behind the 455 for a reason so a stock rebuild probably won't last too long unless you baby it, but that's not why you drop in a 455.

Svnt442 is right drop the th400 in and you will have a winning combo! But the omega was the only olds that never got the 455 so some thing has to give... On the 77 it may be as ez as moveing mounts... But i dont see it just sliding into place... Let us know how it goes