A833 Installation Opinion

I've done it both ways (though not lately)
It is easier to get the trans, clutch disc, etc lined up when the engine is out of the car. But then you would have to have the engine out too.

No doubt the iron case 833 is a lump. I first did it while lying on the floor twice when I was about 19-20 yrs old. (buddy's 68 Road Runner and my 67 Barracuda). Mine was on my parent's garage floor in cold February w/o heat (or prior experience) Those 273's had those puny 9-1/4" clutches and mine let go in the dead of winter. My buddy's was outside also in the winter on a snow-covered and muddy gravel driveway. He had tried for several days and couldn't get it done. We used nothing but muscle and did it pretty quickly. He talked about it for years after. But I digress.

You need to get the clutch disc reasonably centered and then clamped with the pressure plate. I would cut the heads off a couple hex head screws and thread them into a couple of the mounting holes in the bell housing creating a couple of guide studs. That way you can finagle the trannie a bit w/o letting the weight rest on the disc. You'll have to rotate the input shaft or trans a bit to get the slpines lined up then it slips right in. A trans jack, or floor jack adapter, would be handy to lift the weight but it still has to line up. Otherwise you need two guys to lift it.

If i ever get around to putting a 4 speed in my 68, that's how I will do it, on the floor laying on cardboard.