Will a '73 Continental Mark IV tranny fit into a '74 Swinger with a 318?

Wow. Good find. I had a similar find with a '72 Nova. Saw it on my way home from work. Wasn't there on the way in. $3500 on the windshield so I stopped. 35,800 miles on it. 100% original, paint and all. 307, but....a 4-door. His aunt used to park between a barn and a telephone pole and wasn't very good at it. Had some minor damage to front fender that was repaired well. Bought it for $3500. Rock solid driver. Got it up to 110mph, no vibration at all. 5 years and 10K miles later, sold it for $6800. Still kicking myself for that one...
Fender tag is still on mine. Keep forgetting to take a pic of it so I can check codes. My mechanic DOES know transmissions. He just didn't have a chance to check it, before I came home and started this post. DURING this OP, he did check to see if it was the original trans, but I didn't ask him which it was - the 904 or 727. At the time I found the receipt for the rebuilt '73 tranny, I panicked and just wanted to know if it could have been switched out.
Thanks for all the help and comments. Got a feeling I'll have more issues/questions....