Backspacing and tire questions

[mechanic350]

ok so i have been looking all over for new wheels. i want to run 20x10 on all 4 corners and probably run 305/35R20 on the rear and if i can the same on the front if not 285/35R20. only problem is that i have found 2 sets of wheels both with 6.25 backspacing. the first wheel is the Boss Motorsports 338 style wheel 20x10 or the KMC Nova wheels. also 20x10. I have read most of the threads on here about backspacing and offset and wheel fitment. So far i haven't found much from anyone saying whether or not they have done this or if it will work. I have another set of bed fenders to do a mini tub job if i have to. and i do plan on taking my rear wheels that i have off to measure and see how it will fit preliminary before i buy the wheels. any help that can be given would be great. Currently i am running 18x8 in the front and 18x9 in the rear. thanks again for any help

[fast&low]

I am also curious on this?
You might also want to let us know if you have stock suspension or modified suspension?
Is your truck stock height or is it lowered if it's lowered how much?
Static drop or on bags bags?
Thank you

[fast&low]

Sorry you already mentioned 4 inch drop

[mechanic350]

Yeah static drop. 4 in front and rear. CPP spindles and Hotchkiss springs up front. I have mono leaf rear suspension courtesy of the previous owner. Planning on swapping it out for a the factory leaf pack minus a leaf or 2 to get her to sit level.