My gut instinct is that your radiator cap is bad, even though it tested good...or maybe just not sealing well on the radiator fill neck. It certainly would explain a lack of pressure in the system + your overheating.
70 Roadrunner convt. street car
440+6, NOS, 4-spd, SS springs
'96 Mustang GT convt. street car
'04 4.6 SOHC, NOS, auto, lowered
"Officer, that button is for short on-ramps"
