I have to agree I'm a bit "biased" based on the look, spooling characteristics and downpipe advantages of a TT exh flow is a bit deal on turbos and two 3" downpipes flow a heck of a lot

the twins can snug up tight to the exh port and really spool up quick which is important on a street car

I'd pop some LSA heads on it, don't bore it, get some decent rods and pistons and run the twins only problem is the twins are more expensive and can be difficult to package

the good news for your scenario is that 700 is "generally sufficient" on the street and easy to make with a good efficient turbo setup (single or twin) so alot of it comes down to the following

budget
packaging
personal preference

I'm a bit limited in the choices as I have a TT C5 Z06 so I run a ttix kit (very expensive, but performance is great on the street)

what car is this going into? packaging the turbo and what "plumbing fits best" will help you sort out some of what will work best

sorry to divert the thread, but man I dig that TT Z car

very nicely done!

OP >> good luck with your project. my other advice is don't worry about the small difference between a 346 and 370

with the right turbos and tune, either will make all the power you can plant!!!