I'm trying to remove my flexplate off my 350 to fix a leaky rear main seal. But i can't seem to get two of the bolts off holding it onto the crank. Ive tried using different breaker bars, wd-40 and impacts with more torque, but they wont budge at all and the bolts are beginning to round off. I think when i installed this flexplate, i didnt torque the bolts properly. (I probably just torqued them all in a circle)

Any suggestion on how to get them off? I was thinking about drilling the bolts out,

 

Use vicegrips on the gear area with the handles against the starter pad to help hold the flexplate from turning the motor.
You can use some valve laping compound on the socket and bolt head for more grip.

 

try too heat them up a little bit then bang them with a hammer.