Sorry it took me a while to get back online... been busy trying to rejoin the ranks of the gainfully employed with the $5000 machine resting in my truck that's not making any money.
Regarding the Destination line of tires, they tend to be really good for short wheelbase lighter SUVs, and so-so for trucks in terms of tread life. They ride great, and in fact are some of Bridgestone/Firestone's most popular products, but having sold/installed HUNDREDS of sets of that product alone, let me tell you that you probably shouldn't expect more than about 40K miles out of it. Firestone's mileage warranty covers DEFECTS and DEFECTS ONLY for that particular warrantee period (50K, 60K, 65K, etc). Basically, they're warrantee policy says that vehicle configuration, driving habits, vehicle loading, driving conditions, the lunar phase, etc will effect your tread life.
This has the advantage of protecting the company from morons who drive away from the garage and immediately proceed to head to their buddy's place to drink beer and do donuts and/or burnouts in the vacant parking lot next to his house, and returning a month later to say. "hey, my tires suck bro!" I can remember ONE particular arse in particular where I revelled in telling him to buzz off because of the 20 previous visits where we notated that the front end of his vehicle was shot so badly it was INSANE to even CONSIDER driving down the road. When he read me the riot act and I offered to give him a new set of tires for free if we did the front end work (we're talking tie rod ends, ball joints, every moving component ready to part ways with the vehicle). Needless to say, he didn't take me up on the offer and did what most chumps do and called my district. He wanted to smoke another good set of rubber in 25K and come back complainin'... IF the front end miraculously didn't send him into a guard rail at 55mph before his next visit.
Managers at Retail Operations will put immense pressure on sales personell to NOT give pro-rated discounts on new tires that didn't last that full 65K, ESPECIALLY if the customer didn't come in EVERY 3-5K religiously to rotate, balance (with of course the lifetime balance option at $20/tire), check alignment (with of course the lifetime alignment plan for the vehicle), and basically live at the store (your results may vary depending on how much of a doofus the district manager for your retail location is). This puts guys like me, with a military background and not willing to compromise on our values, in the place of pissing people off, or pissing our district off and ending up in the unenjoyment line. Luckily I found myself in the latter, thus giving me the escape velocity required to escape from retail purgatory.
Basically, what I can tell you from my application is that those Destinations will last a good 40K, and probably not any more. In regards to your question of your wheel size, they are probably a 7" wide rim, as the GM/Chevy 16" five-spoke wheels were mostly 7" wide. You could DEFINITELY fit a set of 265's on those. Since you're not really after a "lifted" look and are concerned about the speedometer, you could go from a 245/75 like you've got now and get 265/70s (you'll want to stay with the more common and hence cheaper 70 series profile). Your tires now have a height of 184mm off the bead lip, the 265/70's will have a height of 186... so they should be NEARLY identical in circumference and not effect your speedo.
Hope that helps.