Headers won’t fit in 67 440 dart
I've never used the conversion mounts but I've seen a bunch and their installation seems a little different every time. Dont forget these cars were not exactly precision built pieces. You may quite likely have to bust out the die grinder and modify your mounts or k member.
FWIW I copied the DC k member from the BBD tech pages and used Schumacher headers to put the 440 in my 74. I thought it was a much cheaper and cleaner way to install an RB in an a body.