Shifters and gears

[89GT5.0GIRL]

I bought my car with 4.10 gears in the rear and I wanted to swap them out for 3.73 to get better gas mileage and all that good stuff. I also wanted to get a new shifter. I knew a guy that had a Steeda shifter in his and he said that it was spring loaded and was very east to shift since it basically did the work for you. Any ideas on some shifters. Also my second and third grinds when I put it in gear becasue the guy that I bought it from ran it hard. I was also wondering if just getting synchros was a good idea or if I should just get a rebuild kit for my trans instead? Thanks.