This is an email with pics from a friend of mine in America who's working on installing one in his T3. Many already exist in Splittys and Bays, but this is the only one I know getting the 'T3' treatment.
Actually looks like it fits in there like a glove. My friend Vern in America who's doing this wrote:
The differential is finished - 3.89 ratio, 4-spider positraction.
The T5 is ready to go (He is using a non-standard, rare 5-speed - the usual Corvairs come with 4 speeds or 2 speed auto which are easier to bolt in). I had to re-engineer the sucker. With the help of a
local machinist friend, I replaced the two front bearings, one of which I
had to get from Lamborgini in Italy. Most of the other modified-T5 owners
are adopting my fix, so I guess it is worthwhile beyond my application. I
also sealed it from the diff so I can use ATF in the trans. I'm much more
comfortable with it now.
The engine compartment is finished.
Right now I am working on the shift linkage. The Vanagon shifter doesn't
seem to impart much 'twist' to the rearward links, so I am installing a Vair
truck shifter in the front and am using the Vanagon tube bits with a couple
of u-joints at the trans.
I think a conversion could be done more easily than I am doing it, use of
the T5 5-speed made it necessary to use the spread-front, center-rear
mounts. I think a center-front, spread-rear method could be used with a
stock 4-speed without the problem of the intrusion into the cabin.
The rear mount is a '65 Vair car, it is bolted through to the receiver hitch
for strength. The gap around the engine shrouding will be filled with a
stock Vair engine seal.

Engine & Gearbox as one assembly awaiting install

Engine from below. Looks like a stock install, eh?

Bird's eye view of install

Cutout top make room for pesky 5-speed T5 gearbox (not needed for the stock 4 speed)

Install looks stock and look how much clearance room is left!