Slant Six to Big block Engine swap in a 74 dart sport.

Have you gotten the big block 727 as well? if so the 904 behind the slant will likely be a 904 and will bolt up to the big block. The 727 is about 4 inches longer than the 904 therfore the driceshaft will need to be shortend. That being said you should definately check what rear end is in the car. Likely a 7.25 but could be an 8.25, regardless you should find an 8.75 as the 7.25 wont last long and the 8.25 may not last long behind the big block.

Frame connectors or torque boxes may be a good idea too. Hope this helps!

T