Need help on Turbocharging a 318

I'd try and off the turbo you have and upgrade to a better fit turbo also try and keep it as simple as you can twins for a newbie may be a harder to tune and will require more hardware witch equals more money more headache
Listen to maddart the walbro 392 is a good pump im running one on mine, also do some research you will find some good info on this site but there's not mine of us forced induction guys on this site you I'd recommend the turboforums for a place to start alot of us are on there as well. Response time over there isn't always great but that's where all the knowledge is at.
Any mech secondary carb can be modified for blow through I think there is a sticky at the top of this section hanger18 mods its not hard to do the basic mods but the tuning process is where the difficulty is
One more thing I'd recommend is don't buy anything else till you figure out what your power goals and the correct turbo size for your application it will save you some time and alot of money I changed my setup multiple times until I was happy
Just one man's opinion