Lucky lad.

Sorry to the A-faithful but I'm close to deciding on a G13B.

So you have a torque wrench and think you can build a motor,well luckily an A series is rather tough
But there is a lot more to building a good reliable engine that will make power and keep making it and you will not find most of the relevant information in a book or online,yes you can assemble an engine and it will work.
A engine builder who knows his stuff and knows the engine will always give you a far superior result,more so than even a decent mechanic,but in truth it takes people in the trade at least 15 years to become half decent as it takes that long to experience most of the little tricks and traps inherent in making good reliable power from any engine.
As to the statement about balance ex factory and no need for machining etc that may be valid for some low mileage engine but each engine encountered is different has had a different service history and the owner expects unique attributes for his engine,this totally negates such a blanket statement.
With close on 40 years of building Race Rally drag and MX,Roadracing and Quad bike engines real experience tells me many do not know and worse think they do.
Just finished a customers Engine rebuild,he had his mechanic rebuild a yamaha banshee quad with a stroker crank and cheetah cub top end.
Cost was comparable to buying decent parts but they got Chinese crap off an Ebay seller and it lasted about 5 hours then went bang,machine work was a joke had to throw the crankcases and new crank in the bin,at least his cylinders were saleable.
He now has a 96 HP 421cc reliable engine at a similar cost to what he first spent plus $600.00 labour
But he wasted over $5,000 dollars doing the job twice because he thought he knew enough to do it himself.
Bottom line every Engine has it's little secrets and most will never know them, as it has cost those who do know much time and effort not to mention money to find out they understandably wish to be recompensed for their knowledge.
This is why you use a good mechanic or engine builder,and there are many out there who are not good also.
Listen to those who have real experience and be guided by them and know when to call in the experts and you will both save money and get a better result in the end and that is what counts.
PS a 130~150 HP turbo will mean upgrading other parts of the driveline or you will be on a first name basis with every tow truch driver in a 500 Km radius from home.