Trouble with the Toyota mota here in Britain is that they're not easy to find either. Think they were only ever fitted to one model (IS350? something like that) and obviously the Lotus Exige and Evora. But, if you can find one, you've got loads of power without having to tweak it and they seem to be pretty much bomb-proof to boot.
Then once you've got the engine you need to sort a gearbox...that means either the Toyota E153 5-speeder from an MR2 Turbo - strong and available on Ebay but budget for a rebuild, plus flywheel and clutch, and the motor's block has to be mildly modified to get it to fit. Or there's the Lotus box which is basically an EA60 from an Auris/Avensis 2.2 diesel, but that'll need some modding too unless it's from a Lotus, in which case you need an adapter plate, the flywheel/clutch, special starter motor, intershaft bearing carrier..oh, and don't forget the engine loom and ECU :-O Jeez! Maybe the Alfa's the better choice after all! Haha!

Thing is, you have to decide which powerplant you're going for when you finally give Craig and Lydia your spec as the chassis is different, as are the driveshafts etc. etc. And once you've got that chassis, I don't think you can swap to the other engine (or maybe you can with major restructuring...all things are possible I suppose!)

The Alfa makes for a fairly straightforward build (it says here), but then the route to more poke is expensive. Go for the Toyota and although it might be a bit more awkward and pricey initially, you probably won't want any more oomph and therefore won't spend any more money (on the motor, anyway). But there's always the Komo-Tec upgrades if you do...they're up to 460bhp now...eeek!

As Phil says, up to the individual....!