it all depends on what you want out of it.
personally i think its great u want to stick to b series and they have been proven time and time again to be built proof if done right.
but you really have to plan well, you can price up the internals to your hearts content, but any good builder knows thats only half of it, for a high power b series motor you need lots of mods to all the systems and lot of them has to be custom.

personally i would do a build like this.
get a erl superdeck block (erl can supply the core) its much cheaper than a dart block and requires far less work.
due to wanting to run NA i would go for 9.5/10:1 comp forged pistons, 10:1 is still low enough to run moderate boost levels and still keeps the motor very responsive.
have the block bored out to 84 or 85mm to bring the cc up to the 2000 mark.
some nice strong I beam rods and arp head and rod bolts
go for a milder cam like a stage 1 or 2
get your head ported and flowed.
oversize your valves by .5mm
upgrade all the valve train
get a new intake manifold like skunk2 or edlebrock victor x and a 68mm throttle body
get a cheap exhaust manifold for NA and a custom 3 inch cat back for when you go turbo

now all this will get you a nice NA setup and it would pretty much be ready to install the turbo.
the most important part is what your going to do with turbo size and your mods to fuel and ignition system.

you will need to get 2 different sizes of injectors for the different setups so thats a waisted cost, you will also have to have it tuned twice.
if you want to go past 280-300kw your going to need to change the whole ignition system to individual coils, which is one of the benefits of k series, this is a major cost.
the pcv system will need to be looked at with the turbo motor.
turbo size will be a big factor, i would preferably go for a large turbo like a gt38 or a gt4088r, mainly cause you want to run the lowest boost you can but have the most flow you can.
with the 10:1 you should be able to run 12-14 psi before you start pinging. that should put you up in the 250kw plus range, which is more than enough for any street car.

but to be honest you are going to struggle to do it for 13k, even to boost the factory engine properly will cost you upwards of 7-8k by the time your done.