AC-460 With the torque your 545 is pushing and the rearend change to 3.54, you are getting into running on the edge. The T-56 needs some help with forks, main shafts and 1-2 gears set. Go to G-Force and look up the kit to do this. They up the torque and HP rates to 800HP and torque with better input shafts and cluster of gears. Not cheap, but will hold up over long term. You didn't say what you are doing with the car, racing, autocross, show and shine?? Going to a 3.54 and having a what first gear ratio? First gear in any trans with a 3.00 or higher is never used and a waste of time. I have 3.31 and don't use first with a 3.06 custom trans. Down the road I may drop the rearend to a 3.07 ratio. The problem is the lower the gear you go the weaker the carrier in the Jag rearend is. I have a 2.88 as backup If I go racing and blowup the 3.31. I also would change the rearend to the 2.88 with the 6 spd richmond and be OK. I run pilot tires, no slicks, drag radials, autocross tires or Billboards. I would also tell you to look into the new Richmond super street 5 spd. It is more stronger and better designed to handle your power plant. The gears are straight cut and not heli gears with a 20-30 degree angle. Little more info would really help with your questions.
Rick L.