I have a 51 3100 and it has a stock rear end and front stock beam. I did put disc brake kit from CCP. I want to put steel wheels and paint body color. I am using 15 inch tires. I want to put 8 inch wide on rear and 7 inch wide on front. I was wanting to know what back spacing I should use. The best I can tell it looks like about 4 to 4 1/2 . Does this sound about right. Thanks for the help.