Torx head bolt removal in bed of 2012 V6 4WD

My 1999 Tacoma, recently smashed by a tree during Helene, had been fitted (by me) with a welded mount for a winch that sat on top of the forward wall and was braced by 2 angle iron arms to heavy brackets bolted through the bed (near the wheel wells) to other brackets bolted to the frame. It was a successful setup for winching logs that sometimes were heavy enough to cause the the suspension to squat under the weight but never pulled on that bed wall. I salvaged the pieces of that setup before the insurance company took the totaled truck away. I would now like to refit it to the 2012 Tacoma I bought as replacement. The problem is that unlike the 1999 truck, this one has more attachments to the the frame that are not the same on two sides of the truck so that the brackets I used before will not work. On the other hand there are substantial looking Torx head bolts (with wide diameter mounded heads) in the bed that are already attached to the frame through extended brackets underneath, two of which are located where the brackets could be attached to link to the angle iron braces (that will be a bit longer than the earlier setup). So far I have not been able to budge the bolts, even with a 1/2" breaker bar and the proper Torx socket. They are somewhat rusted on top and probably underneath. Before I go all in to remove those bolts, can anyone tell me if there is any risk in unbolting them, and if not, what their diameter is so I can decide if they are heavy-duty enough to do the job.

 

You can soak them from the underside in penetrating oil.

Big impact from the top (with you pushing your weight into it so the bit doesn’t slip) is the best way to get these out.

 

I believe they're M12 (12mm diameter) T55. I removed mine to add D-rings and they put up a decent fight due to some rust.

 

Impact worked on my rig. I can't recall if I soaked with penetrating oil underneath before hand or not...

 

Thanks guys. Good to know they will come out okay. I'll soak em topside and under, and then put the impact wrench to em.

 

Yup, the biggest impact gun you can find. A breaker bar or small impact gun won't do it. I didn't soak mine.