I just bought a 77' F250 High Boy 351m and it needs some work. Other then a few wiring problems and a flat tire it has a thrown rod a crappy carb and the timing is way off. They said it would not be very expensive to fix but i was thinking instead of upgrading to the 460 with a c6 trans. What all would i need for this other then the engine and trans?

 

Does it have a C6 in it now, or a manual?

 

Welcome to the site.
While you may hear very different opinions on what should be done, I can only offer my own on the driection in which I wouold go.
Since the 351 is hurt, and needs to be removed and fixed, I would consider the cost associated with the repair, and the costs associated to upgrade to the larger displacement engine. Personally I would never even consider fixing the 351M, and would run right for the 460 and never look back. I have some 400's that run well, but they are still no match for an equally prepared 460. No matter what you do to it, the 335 series engine does not have the same capabilities as the 385 series.
This is part of the reason why the 385 series (429 / 460) upgrade is so popular. Combine the fact that the transmission bolt pattern is the same, makes for quite a simple swap.
If you have a known to be bad rod, then other components in this engine are going to have some issues. If the shop told you that the fix would be easy and simple, probably suggested that the one bad rod be replaced, and this sounds a little on the shadetree side. I would not feel too comfortable replacing one rod, or one bearing, or any components that are so critical.

Issues regarding this swap include:

Engine mounts
Exhaust
Accessory brackets.
Cooling system.
Flywheel and clutch components if equiped with a manual trans.

 

its a 4 speed right now. Ive heard the 460 has way more potential and was wanting to upgrade to it anyways this just gives me an excuse with the wife lol.

 

If that is the case, then we should also mention that you reeeeeaaaalllllyyyyy need a 500 plus cubic inch stroker! Yeah, explain to the Mrs. that you cant go without at least a 521 inch engine, and see what she says. Lol. You are welcome to sleep on my couch for a day or two if you have to. Good luck.

 

Hehe a little outta my price range lol i think i got enough for a 460, c6 trans, a set of rims and tires (16.5 tires hard to come by) and a lift. How high do you think i should go on a lift? this is my first truck and well shoot im gonna go mudding lol. My friend says its really too heavy for mud riding but i figure a few sizes bigger on tires and it wont have anything to worry about lol.

 

Hey i almost forgot to ask should i stick with this 4 speed or go to the c6? i havent really been able to test this trans and see if its any good or not. We only got the truck running for a lil bit my friend had to spray starter fluid to keep it running.... yea he caught the carb on fire. lol i thought it was funny (carb was going in the trash anyways). But i do know this he said a switch for the trans is out because u can crank it without holding the clutch im wondering how that would effect the driving would the clutch just stay engaged? if so im not going to get very far.

 

Those are my thoughts exactly! I also have a 1977 that had a sick 351m. I built a 460 for it and kept the 4 speed. That 4 speed is a damn good trans and the bell housing from the 351m will bolt right up to the 460. I would keep the stick shift, it's less work and I'm just not a real big fan of autos.

For the issues listed above here is what I did.
Exhaust- L&L fender well headers then bolt pipe to that then bolt mufflers to that, no need for any bending and you have dual 3 inch exhaust.
Accesory brackets- made my own.
Cooling system- my truck had a super cooling package and already had the biggest radiator I've seen in a 73-79 so I did nothing. I have autometer gauges, the truck has never got hotter than where the thermostat opens.
Flywheel- the guy I bought my 460 core from gave me a flywheel and clutch.

 

Hey on not pushing the clutch in to crank is the tranny in gear? Hows about the t case? Every thing in gear drive shafts complete? If any thing maybe a bad clutch not bad 150 to 200.

Lift go four incher pretty cheap and easy install.
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