this is only constructive criticism and a little food for thought .....
you sound like your selling the wags cos your not really happy with it or the slow progress and the hassles it's been havin ??
trying to build an A12 with a turbo stuck on it to transplant will only bring more unhappyness as an end result ....
leave the A15 in it, swap in a milder cam and drive it as your daily while trying to sell it.
if your that keen on the turbo idea, start building one on an engine stand, or instead - buy a new A15 and give it a better rebuild than the last with the knowledge you've aquired to date, while saving a little cash to go to the new project, once the wags sells you'll have extra $$$ to do some bigger stuff .....

just a couple ideas ... good luck though, with whichever route you choose