This is where MOPARTS gets tunnel vision...and why most MOPAR guys are slower than the Brand X guys....

Someone asked about fitting a T400 to a B body, hes looking for info, what needs to be done.
Instead of helping him, you guys are chastising him, telling him a 727 will work, and he don't need a 400 etc etc
here some facts....

THE aftermarket is geared towards....T400, not 727's
COnverters, parts etc are all cheaper and more readily available for this trans, because almost everyone out there is using it.
Don't let your feelings get in the way....lol

honestly, a Rossler t400 may be overkill, but guess what, it will be THE LAST TRANS HE EVER BUYS.....keep up with fluid changes and it will literally last forever. I have a Rossler T400 for over 10 years, and still going strong. I make 915 on motor and 4-500? of nitrous on top

Clanton, to put a T400 in an A body, I fabbed a crossmember between my frame connecters. On the original crossmember, the part that passes above the trans I cut that back for clearance and fabbed a 16 ga flat steel to box it back in. Depending on how much cage you have that may not be necessary.
Any more questions ask, I did not do anything to the trans tunnel itself other than trim the lip where the floor and the firewall meet.
Hope this helps

PS : You made a great choice for a trans/trans builder, good luck