Cool wagon, my wife hates wagons, so I am SOL. Smart move going to a 4L80E, the 4L60E sucks behind any sort of power. I plan on 3.90 gears and 29 inch tall tires to make the deeper .75 OD more ideal in my 70S.
The throttle body flange/inlet was opened to 92mm to match the Warr TB.
One of my biggest concerns is with over porting the manifold (ie. shortening the runners may cause a reduction in low-end torque) so I approached it with caution. Effectively I only removed the NVH tube and smoothed the rail at the runner openings to be as close to even as possible.
One thing I did leave in was a piece of the ramp at the halfway point, this might help kick the air up off the floor toward the rear runners (or it might not do a damn thing).
The runner outlets were squared up to 1.05" wide and the gaskets opened to 1.07" (removed the silly ramps) to closer match the TSP heads (1.075") and allow for an easy transition and misalignment issues once bolted down (things are never perfect).
Another reason I am not too vexed about going full out on this port job is pretty obvious: zippy juice.
All this talk about 4L80Es in wagons reminded me I hadn't done anything with mine. First I cut out the F-body cooler lines since they were leaking and are not compatible... and made a mess. Then I got to degreasing the case... and made a mess.
Next up was chopping off the ears and any offending protrusions... and made a mess.
Lastly I slammed the beast into place and started test fitting things. I am pretty certain this is going to screw a lot of my previous work up. FML - oh well, built not bought.
Based upon my initial assessment and some basic fact finding/math the 4L80E swap isn't as clean as one would hope.
The case length difference is 1.343", meaning the driveshaft will need to be shortened by the same length. No surprise there. It does suck that it makes the current driveshaft loop useless.
The real problems are with the pan length (and associated width) and the mount location.
So that is a difference of 4.3875", and what that causes is it put the pan right into 4L60E cross member. Which brings us to the mount which, unsurprisingly, is 4.25" further to the rear. So looking at the graphic below it doesn't appear that there will be any interference between the exhaust and the new transmission (for reference/scale the cross member is made out of 2x3 box).
I am still on the fence about chopping up the G-Force cross member to suit, given that I know the exhaust fits around it. Or just start over. Sigh.
The 4L80E is a great unit, nearly indestructible with small upgrades. But your list shows what even a good used trans will cost, a lot. And the dam trans is huge, as your measurements show, good luck fitting it in and show us your solution. I will probably throw a BOP TH400 short tail at my 70S to start, there is no such thing as a strong, cheap OD trans install. That means a yoke change and move the cross member back, Transgo with dual feed and a $300 converter. Problem is any OD that fits easily, the 2004R or 700R4/4L60-70E needs about $1500 worth of internal upgrades, just parts, not labour plus a good converter which isn't cheap. The 4L80E should allow you piece of mind but still costs an arm and a leg and a big install headache.