personally, if i had the funds to fund a ca18 install i would rather concerntrate it into a wild a15.
I think a lot of people underestimate the fun that can be had in an a15 1200.
Light and powerful is where its at.
Even an a15/14 with 140hp would be a blast to drive on the road.
The ca isnt the heaviest engine in the world but it adds up. Engine, gearbox, bigger diff, much larger brakes, etc in weight.
Have you ever compared a ca and an a series gearbox? huge difference.

Im alittle cross minded as i wouldnt mind a sweet ca in a 1200 but i think for the price and effort an a series is where i'd end up.
And if you want a turbo, a series turbo setups have proven themselves before as a solid power producer.

Of course this is all just my opinion and its your decison on what you want.