ecotec
I was unaware of the design history with the Ecotec, but immediately understood it to be a good choice for a "modern alternative" engine to go into an Alfa (I was thinking anything 105).
In fact, it is becoming a popular choice also into Datsun 510's - at least among the normally-aspirated fans.
"why not go big" is always a good question, but "why go too big" is also a question worth asking, because suitable braking capabilities (at the very least!) must accompany power increases.
Anyway, the reason I understood why an Ecotec engine might be a candidate had to do with
-1. Availability (in the US there are many models that used this engine, and the associated parts availability. The Pontiac Solstice/Saturn Sky even used (the 2.4 N/A and the 2.0turbo version) in RWD form. The Sky and Solstic aren't made anymore but there are multiple GM vehicles that have used the Ecotec through it's generations - even up to some of the latest direct-injected versions with impressive hp and mpg.
-2. Aesthetics - the DOHC and overall design (as pictured in previous post by the OP) is somewhat reminiscent of early Alfa engines (Nord) -albeit with the intake and exhaust sides inverted.
-3. Design. It comes in 2.0 turbo, 2.2 and 2.4 N/A versions (+others?) yet is a very compact package. The lost-foam casting Aluminum block allows for an impressively lightweight 4 cyl for it's displacement. VVT helps with low-end torque, and for those interested in electronic tuning, EFI-live and other aftermarket companies offer support, and of course there's a large community of enthusiasts already experienced with them. In that era of engine, it seems as is the Ecotec and Ford's Zetec from a few years earlier seemed to be the domestic compact I-4's of choice for kit cars and ground-up builds like the lotus 7-"type" builds. In an earlier Datsun 510, I did a build with parts within THAT manufacturing family and accomplished around twice the original HP and TQ with good drivability, but that was 10 years ago and parts are getting hard to find. I imagine there are some parallels with folks doing twinspark conversions. There's no question that it's a BIG DEAL going with a drivetrain bearing another mfr.'s badge, and regardless of that being "appropriate " or not, the size, weight, stock power levels, wide availability, and fuel efficiency of the Ecotec made it MY choice also to power the next Small RWD car build.