I saw some of those photos of a ca 18det into lagwagons 1000. From memory, its about $2500 for a front cut silvia. You could do a direct transplant touching nothing and I reckon it would come out about the same. as the a15 jobby.

In my guesstimation of 15 turbo job, i reckoned
rebuild a15 - $1000
computer - $1000
turbo - $800
custom pipe work to make it fit - $500
misc - $800
= $4100
plus everything else!!
The a15 was planning on going efi, crank angle sensors, rollers, double valve springs etc, the whole bit. so basically a modern efi motor, but with the heritage and simplicty of transplant.
But with hp figures of about 170hp at the flywheel for a standard ca18det, i would think that you wouldnt get that sort of hp from the a15 without serious mods.

Is my logic logical??