I know there are cng and lpg kits availible for your unit. The only issues would be tank size (bed or underbody mount) and age of the engine. If you are planing on doing or have done a rebuild then go for it. I have a flex fuel sport trac and I have run E85 in it and was pleasantly surprized with proformance but my milage drop and avg of 3 mpg
E85 is way easier to do, CNG the most difficult. What is the motivation, environment or economy? CNG is the cleanest by far, but most limited as far as range and refueling infrastructure. LPG costs as much as gasoline or diesel around here, so there is no payback.
Stock compression ratio is 9.2:1 which is not enough to gain any mileage or power gains on CNG or propane. I wouldn't do it unless propane is REALLY cheap in your area.
To gain from CNG or propane, you can shave the heads as far as possible to bump C.R. While doing that, get hardened valve seats installed in your head. This will probably cost $1000, but check into rebate programs in your area.
Which conversion you go with really depends upon the price of each fuel in your area, its availability, and how much fuel you go through annually for its payback.
There are V10-specific LPG and CNG kits available but none are EPA-certified so they would be difficult to be commercially installed in the USA. CNG systems are generally not available to the DIY installer so CNG conversions are even more difficult. I have no idea if there is an EPA-certified E85 kit available but I would expect that it would easier to DIY install it.