[S.J.SLEEPER]

The Lt1 is going to be your airflow restriction.... lol....sorry, just had to.

Seriously, use this to put things into perspective.
o.k. turbocharged engine has many different values to figure, but without going nuts and losing you on airflow, cfm,psi, pressure ratio, velocity, etc.. etc..etc..

A 3.5" intake tube will flow 1000cfm+ N/A, in which under pressure (turbo=psi)
multiplies the amount of cfm the same 3.5" pipe N/A will provide.

So lets say 1200cfm is the airflow that is going to be coming into your engine via the turbo.
150cfm= 100hp
so 1200cfm = 800hp
Which I believe is what your looking for.

Your 76mm probly flows in the neighborhood of 98-100 lbs/min which is approx: 1500cfm. which will put it exactly where you wanna be having quick spool, and 700-800hp with about the same or close in TQ.

Remember that the size pipe/inlet plays apart in velocity & psi also, the larger the pipe/inlet, the more psi it takes to "fill the pipe" and slows down velocity.

I would stick with a 90mm TB & the elbow,
Here's a tip, re-drill the elbow's mounting holes so you can turn it towards the passenger tire, this will fix needing a huge cowl hood and will give you more room to run the intake piping.