[Formulajones]

Youve got other hurdles first

How are you going to fit a 1st gen leaf spring rear in a 69 4 link a-body? Not only that but the 1st gen f-body rear is narrower than what your GTO originally takes. By about an inch or so.

You're better off just getting a carrier and gear set for the Chevy 12 bolt and keeping that in the car.

[skunkfunk]

Originally Posted by Formulajones

Youve got other hurdles first

How are you going to fit a 1st gen leaf spring rear in a 69 4 link a-body? Not only that but the 1st gen f-body rear is narrower than what your GTO originally takes. By about an inch or so.

You're better off just getting a carrier and gear set for the Chevy 12 bolt and keeping that in the car.

Indeed. I've already tapped out on doing this project myself - I am getting a bit lazy lately, but probably would have attempted the transmission conversion if not for this rear end issue as well - and if we go that route the mechanic's plan is to measure and weld. I'll bet it takes him a few tries.

I figure if one inch kills the build, I was already in trouble...

I was thinking if I go with the close ratio transmission and the f-body rear, I can save that 12 bolt and build it with the correct gearing for whatever the next engine is. That 400 is a 20+ year old build and has to be around 100k miles by now. Maybe it'll outlast that rear, maybe it won't.

I am open to being convinced to just do the 12 bolt now and get it over with, though.

[Formulajones]

Me personally I wouldn't want to muck up a 69 GTO with a cobbled f- bod rear, especially when it already has a perfectly capable GM 12 bolt already under it. It's way stronger, do it once and be done.

Just go with a 3.55 gear, it'll work with either tkx you choose and works well with any larger engine you might build in the future.

[Formulajones]

Me personally I wouldn't want to muck up a 69 GTO with a cobbled f- bod rear, especially when it already has a perfectly capable GM 12 bolt under it. It's way stronger, do it once and be done.

Just go with a 3.55 gear, it'll work with either tkx you choose and works well with any larger engine you might build in the future.