How about an adaptation to take the old Alfa Twincam with rear transaxle
gearbox.

That would be awesome. Especially if you got hold of a 75 Turbo engine
for it.

I've driven one of these with a Burton race engine (1700cc I think)
fitted. Truly awesome. Much as I like my 2.4JTD, this is the wrong
place for it - it's too big and heavy. Even if you did fit it, it
would be so quick you'd need to fit some kind of auto box or your
hands would be a blur changing the gears given that 4500rpm is useful
top rev. The 7 is best with a lightweight power unit (preferably a
screamer!). YMMV.

I would think that the big problem would be adapting these engines to
RWD. Here in the States, there is pretty big business (in the Alfa
community) in replacing tired 2.5 liter GTV-6 Alfetta engines with 3.0
liter units out of 164s (the last Alfa sold here in the US). The reason
why it works is because when you pry the transmission case off of the
bottom of the of the engine block, you have a pretty standard Alfa V-6.
The oil pan for a RWD GTV-6 or Alfa 75 3.0 fits perfectly; you just have
to drill and tap and few more holes. Then you take the flywheel from
your old engine and bolt it onto the 3.0 liter 164 unit. You do have to
do things like move the distributor from the rear of the cam box back to
it's original upright position on the right front of the engine
(passenger side here in the US, driver's side in Ol' Blighty) and some
minor engineering needs to be done with the intake manifold and plenum
due the the way they were designed in the FWD six. I've even seen a 164
24 valve fitted to a GTV-6 too, but that means even more re-engineering,
but the block's the same so again, the GTV-6 2.5 liter oil pan fits. The
results, though, in these light cars. is worth it, especially the 24
valve with it's 240 BHP! I ought to know, I've a GTV-6 (86) with a 3
liter, hot cams, increased compression and a re-mapped FI ECU. IT flys!
0-60 MPH in 5.8/5.9 seconds, top speed 155+. Yep it goes.

But I digress. The reason that such an FWD to RWD conversion is possible
here is because Alfa hadn't changed the block and the RWD bits from the
earlier incarnations of the same basic engine still fit. You won't have
that kind of luck with modern Alfa engines like the 2.0 TS and the 2.4
JTD because there never were RWD versions of those engines built. You'd
have to have an oil pan fabricated as well as an exhaust manifold (the
2.5 Liter GTV-6 headers fit the 3.0 Liter 164 12-valve engine perfectly,
but they won't fit the twin-cam, 24-valve heads) and god only knows what
else (engine mounts?). This makes such an engine swap really expensive,
but I bet a '7 with the Alfa 2.0 liter 4 would scream!

In a similar vein, I sometimes wonder what my 1.8TS engine would be like
in my better half's MX-5. OTOH, I'd like to try her six-speed gearbox in
my 156...

Halmyre

Well, it's not a 2.0TS, nor a 2.4JTD... how about a V6? ;)

http://www.xs4all.nl/~hdeheer/temp/kitcar_v6_1.jpg
http://www.xs4all.nl/~hdeheer/temp/kitcar_v6_2.jpg
http://www.xs4all.nl/~hdeheer/temp/kitcar_v6_3.jpg

I shot these pictures on a meeting of a dutch Alfa Romeo webcommunity.
Unfortunately I don't have any technical details, but if I recall collectly
this car is owned by one of the guys behind http://www.squadra-tuning.com/,
I think his name was Stephan or Stefan? Maybe some of my dutch friends here
know more about this beast!