Anyone have any tips on removing the fasteners from the collector outlet flange? (Where the catalytic converter bolts up to)

I'll ultimately be doing this in my driveway on ramps, with hand tools. I have enough extensions to get the socket up there, but no amount of penetrating oil, heat, muscle or gratuitous profanity seems to want to budge these bastards. I'd like also not to break the studs/bolts (whatever they are), as I'm not real fond of trying to drill and tap holes up there...