The TBSS intake is a 4 bolt pattern.
I tried to fit the Volant intake tube to the 90mm this weekend here are some pics.

 

Why on earth would you even want to use a 78mm TB? the whole point of putting the 90mm intake on is more flow. The 78mm TB just creates a bottleneck and is pointless. Just keep the stock intake on if you're not willing to upgrade the TB.

 

The way I see it is that the stock intake don't hardly gain anything with a 90mm TB, so that tells me that the intake itself has a very big part in the air restriction. A polished (by the way, we're gunna do that) 78mm throttle body flows approx 940cfm... That in my opinion is plenty of air for a little 5.3. And I never did rule out the idea of a 90mm TB, I just said we don't quite enough money for that at the time. We want to see the difference in the intake in itself as of now. We kinda ran short of money cuz we're buying tbss intake, tsp cam, hardend push rods, and arp rod bolts.
We're gunna see wht a 5.3 can do, our goal is full boltons, big cam, tbss intake w/90mm TB, milled and slightly ported 706 heads, 3600 edge stall, and 4.10 gears... we're hoping for mid 12's all motor.
His current setup is full boltons(minus under drive), 221 558 cam, 3600 stall, 4.10s, and he ran 13.022@102.4 density corrected... He ran 13.4@99.6 at 2400ft

 

Did you have to change alot of stuff to get it on?

 

90mm T/B
Vette Filter/Regulator Part Number 10299146. It has 2 males and 1 female.
Custom T/B cable bracket.
Intake tubing and pipes.
I added 42lb injectors.

 

Also for the 90MM to 78MM T/B I think MagnaCharger makes a conversion plate, but not sure if they sell it without their supercharger kits.

 

Sell the ARP rod bolts and get the right TB then. You're wasting your time/money with those.