MF 12 Baler - Tooth Replacement

I recently bought a "legacy" MF 12 baler in good shape. Some of the pickup teeth need to be replaced, but in order to do this, it's clear I have to remove strippers. However, these are

secured with round head, flat blade screws which are frozen in, having been there for 50+ years.  I've tried PBlaster and heat no avail as it seems like the oil cannot penetrate past the screw head/stripper surface and there's not enough space to get a straw up between the underside of the stripper & the hole. Too much force on the screw will strip the slot;

I sure don't want to be stuck drilling them out. So many of these balers being out there, I assume someone has dealt with this before. Any ideas appreciated!

MF 12 Baler - Tooth Replacement