I'm usually not a big proponent of Toyo tires as they are spendy and not worth the extra $$$. Often you can buy a better Michelin tire for cheaper from Costco. Les Schwab is the biggest seller of Toyo tires but they charge lots for cheap tires. So buying a set of M-55's is probably going to hurt. LS does have good customer service and a lot of stores in the west.
However, the Toyo M-55 has earned a reputation as being the toughest light truck tire that one can get up on the very rugged Alaskan/Yukon gravel roads and many other places in the world where tire damage is a big issue. It is a commercial traction/all terrain tire that will not get many compliments for having a smooth ride or being civilized. They are all about getting you there and back. If interested, please do some research on the M-55 and post up what you think.
About going up to 265 75 16 load range E tires: I don't know if the wider size will fit for sure on your Savana. I do know that Costco is pretty conservative about up-sizing tires so probably it is OK.
The 265 75 16's are 32 inches in diameter and the stock tires are about 30.8 inches. So your clearance will be upped by 6 tenths of an inch. You could also go with go with the 235 85 16 load range E tires, they are 32" also. I'm a bit of a skinny "pizza cutter" tire fan myself. I'm guessing that you will go for the 265's for the flotation, for good reason.
I just ordered a set of front Sumo Springs solo bump stop style spring helpers. Pretty cheap and look super easy to install. While they will not do what most folks think as "raising" your rig, they should reduce the sag of the front end, especially when one is bouncing a bit while navigating rugged roads. Since we are talking about a 2wd van, crawling along at super low speeds is sometimes not an option as some momentum is required where a 4wd could go a bit slower w/o getting stuck.
Sumo Springs link:
http://www.truckspring.com/products...xpress-GMC-Savana-Solo-Front__SSF-204-47.aspx
I'm having a Detroit True Trac limited slip differential installed this week.
An aluminum front winch bumper and winch, with synthetic line to keep the weight down, will be installed the following week. That is why I am getting the Sumo Springs. Hoping that my front end will be no lower than stock with about 90 pounds extra hanging off of the front end with the Sumo springs doing their job.
It is interesting that we are both thinking somewhat along the same lines again.
...The less bounce the better - it's the bounce that often is the problem. Installing the Bilstein shocks definitely helped with that but I could still use less bounce. I wonder if having them on puts less pressure on the suspension? Which I have heard is a weak area for the GMC/Chevy's. 
