Slick 60's

Ok Iam changing frames on my unibody Iam using a truck frame so here's my question if I leave the bed on the truck frame and mock up my rear end Iam putting 20x10s in the back and was wanting to know so I can get the rearend cut and what off set to get on my wheels sorry for sounding stupid

Dang 50 people have looked and not one reply THANKS GUYS

Robert.
Your first post with the questions wasn't stupid at all.
It made sense to me - I think.
Problem is it looks like you are breaking new ground - go for it - but I have never seen or done this.
It is just that I and 49 others just don't have the answer to your unique setup.

There are a lot of different things that will impact the offset and backspacing of the wheel, such as what truck frame you are using, size of the tire etc. Its not really a simple answer. What size lip are you hoping to have on the wheel?

There was a long thread about this about a month back I think. I will look...

Not a stupid question at all. The stupid questions are the ones you don't ask.
The reason no one answered is that no one I know of has tried this without completely notching and rebuilding the frame for air bags. In this case, it also means a project like this is one off. You're on your own.
If I understand, you want to put 20" rims with a 10" width on your truck.
Before you spend a ton of money on something that might or might not work, my first suggestion is to find/ borrow a 20" rim with a tire like you want and take measurements. Width of the tire mounted on the rim. Overall height of the tire and rim. Lay a 2x4 across the back of the tire and measure the distance to the mounting hub.
Then, using more straight edges, measure the area in your wheel well from the outside lip of the wheel well cutout to the inside of the wheel well.
Measure the mounting surface of the brake drum to the inside and outside of the wheel well. From there on, simple addition and subtraction will tell you:
1. if the wheel will fit without tubbing the wheel well.
2. since you need to center the wheel in the fender well, you can subtract from the width of the wheel center to determine your offset.
3. you will almost surely have to roll the lip on the fender well or find a way to bulge it out to keep from scrubbing the side wall, but measuring and drawing things up will save you a lot of time, money and grief.
What ever you do, don't start cutting things until you have it all worked out in your head or better still, on paper.
Good luck.

Also, when you consider the width of the wheel and tire, don't forget you have to compensate for the bulge in the sidewall of the tire to get the actual width.

Thanks guys

I have a rear end 66" rotor to rotor (wheel mount flange) and 18x9 wheels with 6" backspacing and they fit perfect under the rear fenders. So, you could do that (1982 F-100 5 on 4.5" bolt pattern axles came on those) or subtract an inch from each side of the axle making it 64" wide, but use 9" wide wheels with 5" backspacing, or a 61" axle (like the slicks have) and 9" wheels with 3.5" backspacing and that puts the wheels in the right place.

If you want to use 10" wide wheels, there looks like plenty of room for another 1/2" outside and inside. That said, a 20x10 wheel with 4" backspacing (based on the 3.5" mentioned above plus extra 1/2" of wheel width) should fit right in there.