My 1980 300 went 350,000 miles ...the carb was only good for 60,000 at a time however....a swap to the 2 barrel helped a lot as well and with a 290 rear end got 24-26 highway in the short box.....

It was also my first van built with bed, cabinets and floor of 3/8 plywood in stead of 3/4 inch , so I saved a ton of weight..

I swapped from a 300 sixer to a 351w into my 83 years ago.

It was easy, only because I pulled the 351 from another van.

Oil pan and pickup,
front motor brackets,flywheel,driveshaft and radiator
300 is different than the 351 . The flywheels dont interchange.
Trans was the same had to move the crossmember forward and tweak the shift rod if I remember correctly.

Id keep the 300 with the current cost of gas.

I used to get 15 MPG highway with the 351/C6,3:00 rear.

Re-curved distributor,performer cam,shift kit,dual exhaust,flex fan,good tires.

I'd keep the 300 also with gas going UPPPPPPPPPPPPPPPP

A 300 with injection will go beyond 300,000 miles, a friend got 20 MPG with a C-6 transmission in his 95 E-150, the odometer has 346,000 miles on it and hasn't worked in 5 years, it's sluggish, but likely due to the factory injectors and check engine light. The 351 was great when gas was below $2 a gallon, it's heading for $4 now, hotrods aren't affordable.

I have a 351W in my 89 Ford, and I am seriously contemplating swapping it out for a 300 when I go to reinstall the AOD transmission. I would definitely keep it fuel injected, too.


The 351 is fun, but at $4 per gallon I can't afford to fill up 36 gallons every week and a half.

That's too much trouble tho Reed, I was lookin to cram a 351 in my Mid, but the way gas is, I'll either try for fuel injection on it's 302, or an injected 300, that has room for a supercharger.

I have the 4.9 in my 150 and I am pretty happy with it, first time I ever had a ford six. It seems to be a great motor pretty good on mpg too. Mine is EFI.

I must say though, I only have driven it 200 miles

I don't know. I haven't been happy with the way this 351 has run in a long time. I am beginning to suspect an internal mechanical problem. I need to do some diagnostics- mainly a compression and leakdown test to know for sure. Sometimes it will idle smooth, but most of the time it idles a bit rough. It has been running hot lately and has been getting really bad gas mileage (worse than usual).

I wouldn't minding swapping it to a 300. The 300 would be much easier to work on and an injected 300 mated to an AOD would be a reliable and economical combination.

Reed, check the plug wires and for a vacuume leak. I had a similar problem with the Astro , and it turned out to be a plug wire boot ( plug end) that had dried out and cracked letting spark go every where but where it was supposed to.