I have an 87 K5 with 350 tbi, 700r4, 3.08 and 33" tires. I want to put a 12bolt rear with 3.42 gears that I got from a 79 parts truck. front gears also. Will my performance increase or will it stay the same? I also have a th350 mated to a 203 x-fer case. could the x-fer case be mated to the 700r4 without troubles? Thank you for your help.