The 5 speed is longer than a 4 speed so yes you will have to shorten your rear d-line & might have to do some minor mod's to the x-member.
NOT, the L50 and L52 5 speeds are the exact same length as both the L43 side shift 4 speed and the l45 top shift 4 speed
L52 swaps right in with no mods besides some slight trimming of the tranny tunnel IF you had the L43
if you have the L45 as a 81 should have then its a direct bolt in
