Well, I've built two of the 1/48th Hasegawa F-4s and really loved them. 

GAMERA...1/32scale. .that way he can injoy it better ( more) to see up close ..peter 

Tamiya would probably be the way to go.  I believe more aftermarket goodies are availble for their kit than the old Revell 1/32.  Lot of choices in PE and resin to correct errors and dress her up.

Go on ebay and hunt down the Pro Modeler 1/48 F-4E kit number 85-5978. It's actually the Hasegawa kit re boxed under Pro Modeler but at a fraction of the cost of the Hasegawa. It also has extra decals that are of excellent quality.

I picked up mine not too long ago for $30 with free shipping. Keep checking as they pop back now and then.

If your friend flew the F-4E, he will have pictures.  If he's married, conspire with his wife to get a look at the pictures and then, build HIS bird. I did this for a friend who flew them  as Wild Weasels  in Vietnam.  When finished, it had the correct tail codes and serial numbers as well as ordnance for a mission.  I mounted it on a plaque from Michaels and went to a trophy shop and had a small brass plaque engraved "Dewey's Weasel."  Dewey balled like a baby when his Wife and I gave it to him and spent the rest of the evening crawling around the coffee table making "jet noises." I used Monogram's 1/48th scale kit.

If just want to give him a great model of an F-4E, may I suggest the 366th TFW's "Chico the Gunfighter."  Look it up on google.  I know about it because my Father was the 366th TFW's Wing Line Chief.