65 Barracuda Fromula S - what to do

if the 273 is a orignal and trani! keep em! go 360 other than the motor mounts ,oil pan ur only goin have the same problems no matter what motor and its easier and cheaper horsepower! up grade the 904 to same year trani and change converter! ur 904 is worth more on the shelf.and as for the rearend that 71/4 was junk u need to up grade anyhow! i went dana 60 cuz cut down,axles,spool,was same as 8 3/4 center chunk! just my too!