X2 on this one.
mine (a 66 dart) has a ridge inside the heater box that the rod "supposedly" is a stop. DUH 40+ year old "whatever the box is made of stuff" vs metal guess what wins? so after glass beading the rod and chasing the threads on the bolt, I used pliers to hold the rod from twisting and breaking the stop (after I epoxied it back into place:oops:) Also where the bolt went through on the bottom I added a small circular piece of black 1/8" ABS to help take the load. made me feel better about putting the box back in for support and sealing to the cowl.