ga90

ok i have a 90 lx 5.0 with 210,000 miles on her. i blew the rear main seal on the motor and decided to just rebuild it, since im sure its getting tired by now she has had a hard life as a state trooper car. my question is im thinking about going with a cobra intake and either gt-40 heads or the trick flow gt-40x heads. what kinda gas mileage do you think i will get out of this and power gains.
i have a off road x-pipe, 1 5/8 bbk shortie headers, 2 1/2 exaust all the way out the back, flowmaster muffs, no smog pump, bbk fender mount cold air kit, 70mm throttle body and spacer, and shift kit in the tranny. and black majic electric fan.

stang8689

Its Ford Gt-40X and Trick Flow Twisted Wedge. Considering you need bigger injectors and pump probably looking at about 17 if on the highway. I haven't figured mine out but thats what I would say