pulled from a 1980 malibu wagon
90k miles
almost all 90k were driven my my mom … a woman who always drives 40 in a 45 zone …
whats it worth now adays ?
well not much considering its only a 7.5, if it were a 8.5 corpoate it would be work a lot more 
ill give ya 100 bucks 
no, seriously
Negative,all 1978-1983 were 7.5’s.
A common swap for malibu’s is the GN 8.5 and a 12 bolt.
My '79 and '80 Z’s both had 8.5" 10-bolts. I thought the 7.5" started near '82 with the 3rd gen.
the 80 malibu is the “new” design of the malibu @ that point, whre as the 79 & 80 f-bods were still the “old” bodystyle at that point, which could be the answer about that
im guessing 26 spline it be good for the f bod guys till late 87 or so then it was 28