The 14 pin on a Miller is different from a 14 pin Lincoln. There is a 115 VAC output and a contact closure contactor pair in the Miller 14 pin. If Your feeder has voltage control, You will need to change the pot from 10K ohms to 1K ohms., or just not use it, and set at the machine, or with a Miller remote
On the Lincoln, the contactor is pins C & D on the 14 pin and the 115VAC is pins J & A. You need to set up the feeder to close the C & D circut, it is probably able to feed115 VAC to the contactor on older shop machines.
On Your Miller 14 pin Pins A & B are connected to close the contactor. C, D & E are remote voltage control with a 1,000 ohm pot. I & J are 115VAC K is chassis common [ground].
Here is Yoyr Miller manual:
http://www.millerwelds.com/om/o4413k_mil.pdf It doesn't show much.
There is a better chart in section . 5-11 in the 302 manual:
http://www.millerwelds.com/om/o4426y_mil.pdfAs You noted the plugs are different, good thing, as tha available circuts differ.