I polish most wheels by hand wet sand em down to 2000 grit then polish the hell outa them depending on scratches ive started with 220 and worked my way up done many semi wheels turn em to mirrors
But that is a terrible question only you know the fuel economy you can have tow of the same trucks with the same motor size tire size gears and they will still be diffrent
Cant knock the asian parts to bad this is a truck at my work guys ripped off the fender and smashed the hood bought some tony yang or wang brand was pretty happy with the fitment i sprayed the new hood and fender boss found out i can paint may be a good or bad thing lol few lil dings in hood...
I also feel it would be easier and cheaper to swap another 350-305 that's been rebuilt built or junkyard 350s are cheap easy and run along time I know its not your answer but may be better in the long run
He's took it out wheelin biggest problem is when turning no clearance issues when wheels are straight its just on the back of the fender that rubs but I think with the 4 inch you'd be fine