What Did They Do ?

[lou6t4gto]

I bought a 1961 chevy shortbed that someone before me had changed the engine /trans FROM a 283/ cast iron powerglide To a 307 aluminum powerglide. thing is: when they did this, they cut slotts into the trans crossmember to get the trans bolts through, ( the transmission is about 1 " too far back), so the driveshaft is too long to get in. IS a Aluminum powerglide Longer than a Cast Iron unit? could they have used the wrong Engine Mounts? or am I doomed to have to have the driveshaft cut? thanks for your help.