the only difference in the motors are the pistons so I see no sense in swapping the whole motor when all I would have to do is change pistons since I dont know the condition of the other moter i would be getting.my bottom end is all brand newstock ho cam is the best cam for the e6 and e7 heads.
good luck fitting the gt40's on the 86 engine..I can nearly gaurantee you they won't fit.
I had two buddies personally try and put e7's on an 86 motor. BOth failed and had ptv clearance issues when they clayed it and had to flycut the pistons.
swap out the entire engine for an explorer motor with the gt40/gt40p heads.
all you need is a 65mm throttle body with gt40 heads...