well, if you wanted to make yourself a 4-5efhe, you could do it, it'd be a bit of a hybrid.. i have no idea how driveable the engine would be... or if it would even make a difference! your best bet in doing this would be, get a 5efhe head (this will have the uprated cams you need), get it skimmed to give the higher compression,get yourself a 4efte inlet mani, and throttle body if you could find a way to rewire it, but i'd just stick with the 4e one,then get a 5efhe exhaust mani and downpipe an ther you have it! some kind of 4efe/he hybrid! ive had the fhe exhaust mani on my 4e and it lost too much back pressure, so probably not a good idea if your not pushing up the power. not really worth the agro in my opinion. Rich.