It should be fine, 904s are alot stronger then some may think, i've tore up a few 727s behind 340s, but in my 360 magnum dart, it'll retain the 904 that came in it, when or if it goes, i'll just just beef it up some, I had a 73 Swinger with a very stout 370 cu. with a built up 904 & Kevlar bands/cheetah VB, it was a killer tranny & laughed at that 370, so if your 904 is in decent shape (even stock), drop it in & don't sweat it.