Crossmember probem, on six to eight conversion

[dcwoodinv]

Hi all New to the board and love all the great informantion. I am putting a 350/350 in my 72 stepside which was stock with a six. I have my 350 back from the shop and is ready to go in. I pulled the six out today and noticed the tranny crossmember is riveted to the fram and is alot further foward than the one for the auto im putting in. I also noticed the motor mount brackets are further back than the 350. Are these the only differances I will find and how much trouble is it to modify?

Thanks Doug