As long as its a small block/C4 It will swap. Although You will need maverick specific frame/motor mounts, crossmembers and exhaust.
There are only a few rear ends that will bolt in, i have never heard of the galaxie one being a bolt in. Also i cant find the measurements online to compare them to a maverick rear end. But you can always make it fit, by either having it narrowed/widened and having new perches welded on. Along with a pair of modified axles.
If it's a 352/390/427 engine it won't fit A C6 won't fit into that little 70 Maverick transmission tunnel The 9 inch rear will be too wide Of course, anything will fit with a ton of work