You can get the gt-40 of various mustangs in the 90's and of course the lightning trucks and if I am not mistaken some lincoln 5.0's as well. Just keep in mind if they come of a 5.0(302) then the head bolt holes need to be drilled to acept your 1/2" bolts. You may wanna consider the gt-40p that came off the 971/2+ 5.0 exploers in stock trim they flow better than the gt-40 and you do need the special headers that run $220 but if you need headers then that isn't unrealistic and the headers can be used with other 302/351 heads I have actually been told that the special p headers flow better than regular headers due to the path the tubes are ran to avoid the plug angles. Hope this helps some good luck
gt-40 came on a lot of engines the lightnings obviously and the mustang gt's I even think some lincolns had them. The gt-40p only came out on 97 1/2 - 2001 explorers/mountaineer with 5.0 96 down explorer/mountaineer 5.0 used the gt-40 so that would be an easy one to narrow down. I did see a mention of the possiblility that the gt-40 and gt-40p's on the explorer/mountaineers did not have the emmissions ports drilled so that is a minor plus. As smog port plugs are cheap and available.
I finally figured out some credible info
gt-40 have gt stamped on the head under the vavle cover lower right, and above the lower head bolt passenger side front there will be three horizontal lines. The plug angle will be like any other head
gt-40p have gtp stamped under the valve cover to the lower right of the head. Passenger side front lower head bolt there will be four horizontal lines. the plug angle will obviously appear closer to a 90 degree angle compared to the head. Hope this helps
Now a more technical question about the GT-40's. How much better do they flow compared to "stock" heads and do they use bigger valves than them? Since they are coming off later model years I imagine the chamber sizes allow for around 9.0-1 or 9.5-1 stock compressions?
Follow the link, keep in mind that overall the 351 heads in the 80's were nothing more than 302 heads with larger bolt holes so they were overall junk. The gt-40 and gt-40p have around 60- 62 cc +/- combustion chambers compared to the average 69 cc of usual stock heads so yeah your compression will go up. Take a look http://www.jason.fletcher.net/tech/f...a/castiron.htm
I would hate to go here but I think I will just for sake of info. MM&FF did a recent article where they flowed the E7's against the p heads as well as many other manufactueres. Of course they sucked but what they found when they flowed them and then used the formula to figure potential hp they actually exceeded the figures, I would say their thinking leaned towards the way the heads flow improve hp and tq as compared to the actual flow number. They were able to make 350 hp and 400 lb ft of tq from a stroked 302 (333) using the bone stock E7's which are crap in everyones eyes. Their is a place that ports the E7's for $650 including new hardware to flow 219 intake and 151 exhaust and if you figure the stock ones flow 160 cfm+/- intake you can tell right off the bat 400hp isn't impossible from $600 investment on ported E7's. I know you could get the gt-40p's for the same money but the ported e7's would still flow better and you would require more money to port the gt-40p to flow better and if you figure $400 for initial gt-40p investment and $400 to port you just entered aftermarket introductory head pricing and if you look those ported E7's also flow better than windsor and windsor jr. heads. I know there are many ways to look at this so I will just throw it out as general information because I don't care one way or the other depends on your future goals etc. on what you decide, Later