Bubbles in rad HELP!

Late 70s LA 360 in a 73 scamp. Only things I've done to the motor is aluminum intake, 4bbl, headers, and a top end gasket kit.

My coolant is super dirty and getting bubbles in it. I've flushed until clean multiple times and even used the chemical flush and it always comes back. Now that it is warming up outside, the car is warming up too (225-230) after 30-45 minute drive.

Water pump is new, thermostat is new, heater core is bypassed. What gives?!? I've heard about water jackets in exhaust bolt holes. Could this be my issue? I've always had an exhaust leak and put on the Mr gasket set and it isn't near as bad. Oil looks perfect and trans fluid looks great. Radiator looks like it has leaked in the past and could need replaced but would that fix the issue?

Any advice helps!
1st. and easy thing 1st. Top off radiator plum full. Disable ignition by pulling coil wire, whatever. Have a helper crank engine over while you watch radiator filler neck with cap off. If it raises up and runs out you have compression leaking into cooling system, this will show anything MAJOR wrong 1st. Hope it helps.