I've read tons~I still have questions~tire/wheel

[low&slow]

Just to start off, I did do a thread search for Tire and Wheel combos and information regarding sizes and back spacings and I still have questions. So here goes.

I have a '69 chevy c10 long bed. It has stock suspension up front and in the rear. The rear is springs and trailing arms. I really, really want the pro-street look with the fat tires in the rear. I am also building it to be a drag-truck, but it will be driven on the weekends when it is nice out as for it doesn't have a heater anymore.

Anyways, I found a few threads about how big of a rear tire you can go and one post says, "the biggest you can go is 15 or 15.5 inches wide on a 14 inch wide rim with about a 9.5 inch back spacing. Now I'm not wanting to go that wide, but I was just wondering about that if it's true or not."

Another thread about this topic had a post saying, "with tubs you can fit a 31x18.5 on 14" rims w/ 10bs.. wont touch a thing."
Now I am going to tub the bed as soon as I figure out what combo I want for the rear and as soon as they arrive after I order them.

My question is, I'm looking at a pair of 15x12 rims with a max of 6 1/2 inches of back spacing because that's the most B.S. they offer for the style of rim I am looking at and I'm wondering if that is going to be enough back spacing for my truck without sticking out past the bed side if any at all?

Also with the rear tire, I'm wondering if a 33'' x 12'' - 15'' will fit my desired rim size or maybe even a 29.5'' x 11.5'' - 15''? Also, will these tires Even fit under the truck?

Now for the fronts. I'm looking at getting a pair of 15x6 or 15x7. Either sizes don't really bother me, I'd just like something around that size in the front. With it being a drag-truck, I don't think running 15x8's up front would look very well in my opinion.

I'm wondering if say I get a 15x7, will 3 1/2 inch back spacing be to much or not enough?

Also, what would be a few different size tires that will fit a 15x6 rim or a 15x7 rim, as in height and width?

I really appriciate all the help I can get from you guys. You all have helped me so much already with other questions I've had in the past. Just wanted to thank you all again.