Plenty of strap and buckle fans, but whoopie slings are my suspension of choice. A lot of cottage vendors sell complete whoopie suspension kits in the $25-30 range.
However, I enjoy making them myself. Given your size, you might consider using 1/8" Amsteel (2500 lb. breaking strength) rather than 7/64" (1600 lb. breaking strength), though a lot of big fellas are hanging with 7/64 Whoopies.
The general rule of thumb that I've heard is you want a 5 to 1 safety factor. In my case, I weigh 150 lbs., so I'm nowhere near the breaking strength of 7/64" Amsteel (150*5=750). I've got a 10 to 1 safety factor.
With your size, you'd be over the breaking strength of 7/64 Amsteel, and 1/8 Amsteel might be a better choice.
As for tree straps, most folks seem to use 1" polyester webbing, which some cottage vendors list as having a 1500 lb. breaking strength. I'm looking at http://www.strapworks.com and they list their 1 inch polyester webbing as having a 3800 lb. breaking strength. You could also consider 1.5" polyester webbing at 4800 lb. breaking strength.