I'm running a 3.55 true trac with my .83 ratio...5th gear. I have a Tremec TKO 5 Speed manual. I didn't get the .68 5th gear but got the road racing .83 ratio. My rims/tires are currently 15" with a 25.16" diameter(they came with the car when I bought it). Getting ready to put on my 17X8 rims up front/17X11 rims out back. Fronts will be 235/45/17 and rears will be 285/40/17. (11.22 inches wide). Going with Torque Thrust II's. To get to 3,000rpms in 5th gear, I need to be going 80mph

P.S. I siliconed my intake and 2.5 hours later I had her running. You should be fine judging from the pics you uploaded.

Here's a pic of the same rim/tire combo.

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347 Stroker/XE284H(284/296 dur, 240/246 dur @ .050), BG 650 VS Speed Demon, Ported Victor Jr intake, Jack Roush World Product (ported from 180cc to 195cc) Jr Heads(upgraded to 2.02/1.60 valves) 260cfm/190cfm @ .550 lift, 11:1 comp... 450-475HP