You will need a 1971 to 1977 Ford maverick rear this is an 8 inch pumpkin and it is 56 1/2 wide, only 9 inch that will fit is the 57 Ranchero and you'll be hard pressed to find one... That 8 inch will hold up just fine and gears are available from Speedway..
http://hotrodders.com/kb/transmission-rearend/data.html