Well, the answer to the question, "should I do it?" seems pretty obvious in my case. My Bronco currently has a 300 mated to a ZF 5S-42, 3.55 gears, 32" tires. So far I've added an Offy C manifold, 500 cfm 4v, and EFI exhaust. It's perked her up a good bit, but now I'm contemplating the next upgrades.

That next upgrade would be a rebuild + balance job, new cam, and head work. By my back envelope calculations building up a nice little 300 will probably set me back right about $3,000 in parts and machining. But on the plus side...that's about it. Other than a new clutch kit and mounts since the engine's out anyway, it's plug and play. Fair enough.

On the other hand, I was convinced to pull the plug and get rid of a previous project vehicle. Left over from that project I have sitting in the garage a not-even-broken-in-yet 351W. It was built for a pickup, but would probably be plenty hot in a street machine, too - '69 block completely reworked, dynamic balanced, flat top hyper pistons, new pair of later model FRPP X303 heads, roller rockers, Comp XE262 cam, c/r is just shy of 9.5:1. I figure it's probably good for 350-360hp at the flywheel as it sits.

So it seems like a no brainer. I like the 300 for what it is, and a built 300 would be tres cool, but the 351 I've got would run circles around it. Torque wise the 351 kills it from idle to redline. Maybe the 300 would get better mileage, but no big worries with overdrive and a 33 gallon tank.

Otherwise I sell the 351 for maybe fifty cents on the dollar and put it towards a new 300. That seems nuts to me. I'd hope to get enough back out of selling the 300 plus the manifolds, y-pipe, carb to almost cover the cost.

Other than the obvious - SBF frame perches, a new radiator, and new exhaust - what else would I need to do the swap?

 

this is a hard one to say the least. I LOVE the 300-6, its really a great motor and if built well it would last a long time and perform very well. Since you have the 5 speed a gear swap to 4.10's would really wake up that 300-6 and show you a whole new rig at the same time. might make you rethink going the 5.8 route

Now I just had my 5.8 rebuilt which ran me $2300 at cost, should have easily been a $3000+ job. i am running jba shorties, edelebrock efi truck intake and have a .30 overbore with the motor balanced. i am loving the motor and feel it should last me a long time. I just think that everyone goes the v8 route and in your case you already have the 6 with most of the goodies folks want in that motor. Even in this economy i feel you could easily get $2500-3k out of that 5.8. heck even selling the heads alone should net you close to a grand.

being that you dont have efi to worry about that for sure makes this swap easier also.
very very tough I am on the Fence with this one.

i do think a gear swap though would change things in a good way. might go that route first and see. the 5.8 isnt going anywhere.

 

Funny you should mention EFI because the 351 was going to be set up for MAF EFI, so I've got an Edelbrock Performer EFI upper, Typhoon lower, A9L EEC, etc. too. Heck, I've even got a speedo cable that fits into the VSS and the stock speedo. But that would be for another time if I do go through with the swap.

I've been keeping my eye on craigslist for an otherwise nice, cheap vehicle with a bum engine into which to drop the 351, but even then I'd only get fifty on the dollar unless I fell backwards into a sweet Mustang or something. Too many projects was the problem in the first place, I can't justify another anytime soon.

I do like the 300. And I'm not in any real hurry. I reckon it wouldn't hurt to toss the 351 back out on craigslist for a couple of months and see if anyone bites.

 

i dont envy you on this decision but with time on your side that should help. I know you are already aware how rare your bronco is being it came factory with the 300-6. ive looked and looked with no luck here in the PNW for one.

going MAF on that 5.8 would be the ticket for sure. I say find a BroncoII or an early 68-74 bronco and drop that 5.8 into that and make a wheeler out of it.