should I change gears or tranny???

Yea, vans and trucks, Durango's and Dakota's w/360's have them, HD units are a best bet target as 1500 or light trucks may not/probably not have them. But check anyway. Same oil pan as the older 904 or 727 differences still apply. Look for that familur 727 pan on the OD unit and yor good to go.

The trans mount is different, so grab that for possible use/re-working of it. Shorter driveshaft and possible pinion angle adjustment. That's all I can think of at the moment.