I'm thinking of taking out my 4 speed out of my 86 with the 460 and want to put in a 5 speed to try and get a little better mpg is it a easy swap and if so what years match up for the easy swap?

 

Zf-5 from mid '87 to end of production in '97.
(s42 or -47 doesnt matter but it MUST be from a 460)

You need a higher floor pan and the proper crossmember, or move the existing crossmember which can be a pita to drill the upper frame rail.

My 4x4 truck didnt need any driveshaft work