OX
I use 50% acetone with 50% any atf. Works better and less cost than the stuff in a can at 8 buck a pop, get a spray bottle like you use to spray windex. I spray once and wait 24 hrs use heat OxAc, then spray again and wait 24. If it is still not giving, then I get two long box end wrench's and bust it up, if that doesn't work get the fire wrench.
Project looks good, making head way on the grill.
Keep on keepin on
Nut Case
ps I have a 57 GMC disassembled down to the frame scattered between two states. I'm downsizing. No Joy