Broken FD Rear sway bar mounting Bolts
 

Guys,

Long story short, i sheared off the 2 bolts on the exhaust side of the car where the rear sway bar mounts to the chassis. I've attempted penetrating oil and heat with no luck. It looks like I'm going to have to drill out the bolts and tap some new threads. I need a recommendation on what grade of bolts i should buy?

Thanks in advance,
Dave