455 out of Ninety-Eight Going into 1980 Cutlass G Body

GBodyGuy

New member
Apr 20, 2020
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1
Ok I have a 1980 Cutlass Supreme that previously had a 307 in there. The 307 and transmission are both gone and I’m replacing them with a 455 Oldsmobile out of a Ninety-Eight with 21K miles on it and comes with a the TH400 Trans bolted up with and the drive shaft. I’ve been told that this isn’t a simple drag and drop due to the driveshaft or transmission needing to be modified to fit the car. What should I do ? Get a TH350? Will it take this 455 with aftermarket Headers, Intake Manifold and has been done up to push out some major HP/Torque...
 

Kennybill

Active member
Oct 3, 2018
203
127
43
Braceville Ohio
Full size cars (88&98) had long shaft turbo 400. Either have new shorter driveshaft or different shorter trans. Crossmember moved back. Tube Headers that fit are pricey
 

Olds 307 and 403

Active member
Oct 4, 2018
603
213
43
Melville, Saskatchewan
Go manifolds, the W/Z reproduction manifolds or Thorton shorties will fit. What trans do you have now? A stock TH350 with a Transgo shift kit and a few upgrades should survive.
 

TURNA

Active member
Oct 5, 2018
189
95
28
NY
TH400 into a GBody

You need to cut the "ears" off the TH400
Cut the driveshaft to correct length
Use the driveshaft yoke from the donor car
Fabricate a kickdown
Get a Xmember for a TH400 along with the frame extenuation piece

And finally ditch that 7.5 rearend, because you are going to blow it up!!
 
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TURNA

Active member
Oct 5, 2018
189
95
28
NY
I have it all wrapped up at the moment and it is raining.

If its nice out tomorrow I will