Re: 94 F150 - Engine getting weak - options for replacement to increase MPG???
There are some things you can check to see how the engine is doing without jumping to extremes.
First, is to get the compression checked. If the compression in all cylinders is within spec then a loss of power can knowingly be related to needing new spark plugs or even an air filter.
Second, get the fuel pressure tested. If pressure isn't within spec you could simply need a fuel filter.
Third, check the thermostat, or save yourself the time and spend the $10 on a new one. If you remove the rad cap (also can be replaced for $15 if you don't believe it's holding proper pressure) and see a white substance around the rim chances are good the coolant is shot and needs to be replaced. It's best to do a professional flush in this case for best results.
If you don't work the engine regularly, I'd keep an eye on the transmission fluid as overheating the transmission fluid can increase engine heat as they're connected directly. I doubt it's much of a concern but is still there, and is enough to keep an eye on.
To swap in another engine, let alone a new one where emissions come into play, it would be more worthwhile to seek a newer lower mileage truck. If you don't tow regularly anyway, perhaps a smaller V6 vehicle with a moderate towing capacity in your price range can be found.
Just to let you know, you didn't have to include your red light running incident although knowingly you did to brag about your innocence, as if you knew you were guilty I'm sure you wouldn't have brought it up as it doesn't pertain to any of your questions! Cheers.
'00 Durango R/T 360ci 290hp (modded); 138,500m
'06 Pontiac G6 GT 3.5L 220hp; 44,000m
'12 Chrysler 200 Limited 3.6L 283hp; 13,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!