Sawzall!!!!
a buddy of mine has an 85 chassis with an 81 body and a 92 22re and his "secondary backup wheeler" is a SAS 87 xtracab with an 86 4runner body. From what I'm told it wasn't too difficult but you definitely have to want to make it work or it'll ride worse than my 88 xtracab.
You can make it work. Start cutting and post pictures