Why should I not go to an 8.8 rear?

So here is my dilemma. I have an A body 8.75 rear and 489 sure grip that I bought for my dart build. Come to find out the pumpkin has 4.56 gears. Now I have read the entire thread about the swap out to 8.8 off an exploder. I like this idea because it gives me the BBP and disc brakes along with the exact gear I want for under $300. The disc on the rear was not in the OG build plans but would be nice. If I use the 8.8 I could sell the 8.75 and use that money for other stuff I need. I am not 100% oppose to keeping the 8.75 but the 8.8 is starting to make a lot more sense.

My question is, aside from the fact that I am putting ford on a MOPAR, what would be other reasons not to go with the 8.8?

FWIW the car is a 72 dart and I am putting a 340 with x heads. Stock stroke, xe268 cam, headers, air gapped intake and 750dp carb.