this is off the home page, faq's
Which rearends can be swapped into the 78-83 Malibu?
The stock 78-88 A/G body rearend housing (housing flange to housing flange) is 52.125". Here is a list of other common rearend dimensions:
Body Style Housing Width
64-67 Chevelle 54.250"
68-72 Chevelle 55.250"
67-69 Camaro 54.250"
62-67 Chevy II 52.125"
70-81 Camaro 55.375"
82-92 Camaro 55.750"
93-up Camaro 59.250"
68-76 Nova 54.250"
78-88 A/G Body 52.125"
Information from Chevy High Performance Magazine 3/2001
you will have to get rims with probably a 6.5 b/s. i have a 12 bolt from a 66 chevelle and my rims are 5.5 b/s, the control arms for mine went right in with no problem and the spring perches were bang on too.