I would skip installing a used one and get an after market converter. I picked up 2mpgs with one and the little extra work to make the universal style one was well worth it. One scrap one will pretty much pay for the new one.

68 Road Runner, 69 Belvedere, 71 Challenger Vert
340 barracuda, 01 Ram CTD, 95 Ram, 04 Ram, 85 Daytona turbo Z
66 GTO, 06 Magnum RT AWD. 07 Ram CTD, 07 Ram