They may work, I don't know the dimensions of the exhaust ports on the heads. The may seal if the header oval is larger than the square port on the heads, but you could always sell those headers.

You could also keep the heads and use those headers with the comp cam I recommended. The difference between the E7's and GT40X heads with that cam is 259hp/370tq vs 296hp/391tq. The GT40X heads would certainly be pressing the stock injectors to the limit and you pay a lot more for a few ponies and some torque. Where the GT40X heads make more difference is with a more aggressive cam, injectors, and a tune..................

Well, I had the day to be close to the computer. You got decisions to make and maybe more research here. Search? Good luck with your first build!

 

It's not an Explorer motor then.. it could be a bonifide HO or it could just be a plain jane truck motor, you're gonna have to measure the cam to know. If it is a HO then I say don't both with changing the cam, advance it 4 degrees and add 1.7 rockers and run it with those Summit headers.