I own a 1988 F-150 4X4 with an E.F.I. 300 cu. in. in-line six which has been a fantastic engine for the last 150,000 miles or so. It has a 4 speed manual transmission. I now find myself in the position of having a boat & trailer with a combined weight of about 4500-5000 lbs. which is just too much for the 300/6cyl. to pull in the hilly and mountainous region where I live. I am used to the 300/6cyl. getting about 15-16 mpg. with small loads or pulling a small boat and 16-17 mpg. running empty. I have been considering installing a 5.4 litre triton engine to handle the larger boat and still give me decent milliage when running empty. I have not yet looked into compatability between the 5.4 and my bell housing/transmission or even if my existing wiring will match up to the needs of the 5.4 triton. My truck is completely stock...just as it was when I drove it off the dealers' lot in 1988, and everything still works just as it did then. It has not been in any wrecks, and except for door dings, it is completely straight. Any ideas about this swap, pro or con would be greatly appreciated! Thanks!

 

You are looking at an easy $15K in parts and equipment, lots and lots of cutting and welding, months of chasing down wires, months of figuring out wiring diagrams and you still will have an older truck. You literally would have to buy a wreck in excellent shape for the motor, trans, trasfer case, wiring harnesses, cooling, computer and the thousands of electrical sensors. Plus you would need a custom exhaust fabbed up with the 2 cats and 4 O2 sensors, custom drive shafts, a beefed up rearend and the patience it takes to have a homemade truck. In short, don't do it.

On top of that, the 300 is a great motor that makes tons of torque. You are much better off changing the rearend ratio to a lower gear (like 4.10:1) and running it a little slower. Or if you do a lot of unloaded highway driving, swap in a five speed from a similar year F150. With a five speed and 4.10, you'll keep your good mileage (actually better than a 5.4) and you'll have a bulletproof, easy to work on truck.

 

Keep the 6 and add boost. That engine is easy to work on. You can supercharge for a fraction of the cost of changing the engine and if you blow your engine, the rebuilt long blocks are dirt cheap.

 

I think the final number for a L engine swap ( sans labor ) is ~ 10K. This is about 5.4K for the used L engine, and the remainder in in wiring harnesses, GEM and PCM.
This is converting 5.4L N/A to 5.4 L S/C engine, without a trans swap. Add in the cost of the 4R100, and then you are at the 15K number above.

Add to this you would need to swap the gauge cluster with the newer style.

There might be some additional sensors that you would need for the speed sensors, as I seem to recall Ford changed this setup between the years you are talking about ( very well could be wrong on that, memory fad at the moment ).

I would have to agree, rear end swap, and try to find a roots type S/C for it.
With my 1981 F-100 with the I-6, I pulled a 1969 Dodge Polaris for clay track racing, and it went without much problem at all. It was not a drag racing engine, but would pull.
If you are really wanting to swap, then it would be to a 5.8 for the year you have, as not to have the wiring nightmare. Trans bolt up to the 5.8, I forget which is a direct hit.

All in all, this project is about the cost of a used F-150 with a 5.4L engine.