Tire size

I hate having to post this question but after reading so many tire size threads, I have a hard time trying to decide which of the two size tires will fit. 35/12.5r20 or 305/55r20 Someone says they will some say they wont.
I own a 2011 tundra 4x4 crewmax, 4.6L V8 SR5 TRD offroad.* I have installed a 3/2 level lift,* did the body mount chop and trimmed and heated the plastic on the inner wheel wells.* I have a set of the tundra 20x9 BBS wheels that have: offset +50mm and back space 6.97".* I have also installed 1.25" spidertrax wheel spacers.
Can anyone tell me what is the largest all-terrain tire I can install or the largest mud tire I could install.
Thank you for your time

 

Probably read this somewhere else as I'm not too forum savvy. I apologize if this annoys anyone.