Ford Repair: 1993 ford f150 4x4,5.ov8, ford f150 4x4, fuel injection system

Question
I actually have 2 questions if thats ok about the same truck.First off sor some reason the truck stalls when stopping if the ac or defrost are on its fine any other time.I recently had this trouble and noticed that the amps was dropping so I replaced the alternator with a used one from the same type truck.Now I understand there are 2 amperage types a 95 and 135 and could that be the problem or should I look elsewhere.
2.the second question is there anything I can change on the engine to increase fuel mileage it sucks less than 10mpg,I'm fairly handy around cars so changing heads or fuel injection system is not a problem.I would go as far as changing engines if there is a good swap to be made.
thanks bob

Answer
Bob, The answer to your first question, is yes you might've gotten the wrong alternator amperage.  I would recommend that you use any the auto part website using your car vin number for proper part number.

As for the second question, with the car's age and size. I am not sure that there is a quick way to improve mileage aside from rebuilding the engine to its as new specs., but the effort may not worth the reward, your call.....  As long you keep up with the normal maintenance, this would be the best you can do.  Thanks!