I rebuilt a 1961 383 motor withthe stock cast iron torqoeflyte that my customer had installed in his 1963 dart, it had a set of Hooker chassis headers in it made for that swap, they where not race headers I change the crankshaft so he could use a 1963 model aluminum push button 727 and stock converter.
I didn't make the engine mounts but we may have had to make changes to the tranny mount but that was back in the real early 1970s and I don't remember those details now.
I am building a 1965 Dart 270 back half car now that is certified to 7.50 ET with a BB in it for drag racing only, I'm waiting on a local shop to finish the fibreglass molds for the front end and doors so I can mount the motor and get headers made for it
I'm going to use a front motor plate and probably a mid plate to help stabilize the motor movement front to rear BTW, it will have a 555 C.I. B1 motor in it so it has to be done correctly and safely
On your deal if you don't have good fab skills it would be wise to find a really good shop for help on this project