t5 trans swap?

Socal, should be a nice swap. Not sure about your ride, but we put a t5 in my buddy's Fairlane. he is running a 3.55 rear. anything under 2500 rpms in 5th gear and his car chuggs. not enough rpms to make it run. Have to shift it back into 4th to run comfortable until he reaches about 75mph. thats what made me jump up to a 3.91. I believe he has a .68 overdrive as we both have the same trannys and both have 26" tires. May be because of carb and not fuel injected.