I have a 1977 Ford one ton flat bed with dual rear wheels and am considering changing the 351M engine out and replacing it with a 460 crate motor ! I am wondering what would be involved with the switch and if the switch would be the thing to do or not ? The truck will be used to pull a 31 ft 5th wheel travel trailer every once in a while and the rest of the time it will be used to move my antique John Deere tractors around. It has a standard 4 speed transmission that wil stay in the truck also. And the rest of the time it will just be doing some butt totin' ! Thanks any information would be greatly appreciated !!!!!

 

If the added power is worth the drop in gas mileage to you then go for it. You may find yourself needing a heavier-duty radiator with this swap and application.

 

Besides the radiator would I have to change the motor mounts and where would I find them? Where would be the best place to get a crate 460? If you were in this position what would you do? The reason I thought it would be a good idea for the change, one , parts availability later, two,the problem with the351M overheating adn ,three I want to be able to pull a load and run the A/C without the engine overheating ! Any information or opinion would be appreciated!!!!!!!!!

 

Definitely get rid of the 351m. If you get setup right you will have the same mileage as the 351m , but with 70% more power, without really going nut$. There is no replacement for displacement, and of course the durability of the 460 is legendary. Lots of 351m/400 owners will say that a 351m/400 is just as good, but I'm sorry, it's just not true at all, and anyone that has owned a few of each engines will tell you that.
The 460 will use your current bellhousing, you will need a 460 starter, flywheel, and clutch. All 429/460 up to and including 1978 will use an internally balanced flywheel,and 79'-96' will be externally balanced. If you get an internally balanced motor, I've heard that you can use a 360/390 flywheel and starter, and that they are cheaper... I've not physically experienced this. You could look at 460ford.com :: Index in their classifieds and you may find a rebuilt engine in your area. This sites classifieds are fine, but that site is focused on Big Block Fords. Lots of FTE members on there, also.
As far as motor mounts, Jeff's Bronco graveyard can set you right up (I think they're a sponsor?). In Texas, I'm sure you will want your coolant and A/C to work great. You could get a 4-core HD radiator (couple hundred bucks?), or an aluminum radiator ( I would guess $350-$400 new), and you could get an electric fan w/adjustable thermostat ($150?). I've got an aluminum rad. w/double electric fans for mine, but have'nt got it together yet. I think that would solve any coolant temp. issues.
The A/C can get a little tricky on these engines/trucks. You will need short valve covers to clear the humongous firewall box, and maybe either a 1" body lift, or modifying the box a little, maybe not. your compressor will be the same, but the engine block is slightly different, so you'll need a 429/460 A/C bracket. You could just get a Vintage Air kit ($?) that would be more efficient and should be bolt-on, including the needed brackets, lines, fittings, etc... and it will all be new.
Anyway, I'm sure some other guys will have some ideas for ya, also.