question about an olds 455

307 mounts will interchange with the 455 but get new replacement mounts if yours are over a few years old. Get the accessory brackets from the 455, the 307 brackets won't all bolt up to the 455. The alt bracket is the only one. But double check anyway. The last time I swapped a 455 for a 307 was a very long time ago and it wasn't a Gbody. It was a '84 Olds 98. I combined the brackets some how but I don't recall how. The trans you should use is a built up 200R4 or 350. I lean toward the over drive transmission. IMO.
I hope this helps
T

You need to think about what kind of exhaust system you will use.
Headers will be a particular headache. Don't forget you will need a suitable radiator, and if you intend to use the torque available the chassis could benefit from bracing.
The th400 is designed to live with big blocks, even a 350 will struggle without beefed up internals, but building 200R4 transmissions to cope with monster torque has been developed to a fine art now. They don't come cheap though, building one properly means using expensive high grade parts.

Roger.

rustyroger said:

The th400 is designed to live with big blocks, even a 350 will struggle without beefed up internals, but building 200R4 transmissions to cope with monster torque has been developed to a fine art now. They don't come cheap though, building one properly means using expensive high grade parts.

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Very true but, I figured with a '87 307 sbo, he already has a 200R4. Finding a 400, then rebuilding it, then getting a driveshaft cut to fit it, will easily cost about the same as just rebuilding the 200R4. Beefing up the rest of the drivetrain is essential even if it's a daily driver.

The weak rear will be the next thing to break after the transmission is beefed up. The 7.5 can handle DD and light street strip with just replacing the axles and putting in a posi unit. It's been done many times but, once you pass 500 hp the 7.5 is expensive to get to handle that kind of power. It can be done but, getting a Moser 12 bolt would be cheaper. The Ford 9 inch is over kill unless your racing full time. Even then, I'd pick a 12 bolt or Dana 60 over it. IMO.
T

I put a 455 in a 79 cutlass which had the 260. It was a direct swap. I also used a beefed up 350 trans which is holding up fairly well. Don't just drop it in in front of a stock trans. I blew mine apart after a few short miles on the first test drive. I reused my factory brackets except for ac which I don't have. The heater box will probably cause issues if your gonna be running tall valve covers. It will need trimming along the side. And as far as headers, that was the biggest headache. I used a cheap set of flowtechs and modifyed them to fit my car. I hope everything works out well for you. Should be a fun ride when finished.

Fairly straight forward, non A/C brackets will bolt on with the right length water pump and matching pulleys. There are 3 headers, Dick Miller, Hooker and the best American Racing, none are cheap. Get a set of reproduction W/Z big block high performance manifolds. Cheaper and less hassle for a street driven car. Your 7.5" rear will eventually throw spider gears on the street after too many 455 burn outs.

olds307 and 403 said:

Your 7.5" rear will eventually throw spider gears on the street after too many 455 burn outs.

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Yep. The spider gears will be the very first thing that breaks. If you just put a posi in then the next break will be the axles. These are 7.5 rear trademarks. X2 on the W/Z stock manifolds for a DD. That's great advice olds307 and 403.
T

bigt0006 said:

thanks for all the info. my car has the 200 metric transmission not the 200r4

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Behind a big block you might compare it with bringing a knife to a gun fight .

Roger.

rustyroger said:

bigt0006 said:

thanks for all the info. my car has the 200 metric transmission not the 200r4

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Behind a big block you might compare it with bringing a knife to a gun fight .

Roger.

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The 200 on a '87? That sucks. That's not even a knife to a gun fight, it's more like throwing rocks in a gun fight.
The only trans that will bolt directly in place of a TH200 is the TH350. And the hard part about that not rebuilding the 350 to handle the 455s power, it can very well. Finding the BOP TH350 is a super challenge. Especially the lock up version.
Your only real choices are the TH400 and the TH200R4. As stated before, the 400 is cheaper to build but, adding the cost of the custom driveshaft will bring it up to the cost of building the 200R4, which uses your current driveshaft. Which can hold more power is arguable. The 400 will be the popular choice, But there are 200R4s that can handle up to 1000 hp. Mega expensive.

IMHO, I'd start looking for a BOP 350 or the Cross pattern BOPC 350. You may get lucky.
Side note, Don't even think of using a adapter plate on a 455, it WILL flex and break the bell housing.
T